04-chapter4 ospf configuration

Operation Manual - IP Routing Volume Quidway NetEngine20 Series Routers Table of Contents

Huawei Technologies Proprietary

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Table of Contents

Chapter 4 OSPF Configuration .................................................................................................... 4-1 4.1 Introduction ........................................................................................................................ 4-1

4.1.1 OSPF Basic Concepts ............................................................................................ 4-2 4.1.2 OSPF Areas and Route Aggregation...................................................................... 4-3 4.1.3 OSPF Network Types ............................................................................................. 4-9 4.1.4 OSPF Packet Format ............................................................................................ 4-11 4.1.5 OSPF Features Supported by the NE20............................................................... 4-20 4.1.6 Protocols and Specifications ................................................................................. 4-22

4.2 Configuring OSPF Basic Functions ................................................................................. 4-22 4.2.1 Establishing the Configuration Task...................................................................... 4-22 4.2.2 Enabling OSPF and Entering OSPF View ............................................................ 4-23 4.2.3 Configuring the Network Segments Included by Each Area................................. 4-24

4.3 Configuring OSPF Area Features.................................................................................... 4-24 4.3.1 Establishing the Configuration Task...................................................................... 4-24 4.3.2 Configuring OSPF Stub Areas .............................................................................. 4-25 4.3.3 Configuring OSPF NSSA Areas............................................................................ 4-26 4.3.4 Configuring OSPF Virtual Links ............................................................................ 4-27

4.4 Configuring OSPF Network Types................................................................................... 4-27 4.4.1 Establishing the Configuration Task...................................................................... 4-27 4.4.2 Configuring Network Types of OSPF Interfaces ................................................... 4-28 4.4.3 Configuring Neighbors for NBMA Networks.......................................................... 4-28 4.4.4 Configuring DR Priorities of OSPF Interfaces....................................................... 4-29

4.5 Controlling OSPF Routing Information ............................................................................ 4-29 4.5.1 Establishing the Configuration Task...................................................................... 4-29 4.5.2 Configuring OSPF Route Aggregation.................................................................. 4-30 4.5.3 Configuring OSPF to Filter the Received Routes ................................................. 4-31 4.5.4 Configuring OSPF to Filter ABR Type3 LSA......................................................... 4-31 4.5.5 Configuring the Link Cost of OSPF....................................................................... 4-31 4.5.6 Configuring the Maximum Number of Equal-Cost Routes.................................... 4-32 4.5.7 Configuring the Protocol Preference of OSPF ...................................................... 4-32 4.5.8 Configuring OSPF to Import External Routes ....................................................... 4-33

4.6 Adjusting and Optimizing OSPF Networks ...................................................................... 4-34 4.6.1 Establishing the Configuration Task...................................................................... 4-34 4.6.2 Configuring OSPF Packet Timer........................................................................... 4-35 4.6.3 Configuring the Delay of Transmitting LSAs on the Interface............................... 4-36 4.6.4 Configuring the Interval of SPF Calculation .......................................................... 4-37 4.6.5 Disabling the Interface to Transmit OSPF Packets............................................... 4-37

Operation Manual - IP Routing Volume Quidway NetEngine20 Series Routers Table of Contents


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4.6.6 Configuring Stub Router........................................................................................ 4-38 4.6.7 Configuring Authentication for OSPF.................................................................... 4-38 4.6.8 Configuring the MTU in DD Packets ..................................................................... 4-39 4.6.9 Configuring the Maximum Number of External LSAs in LSDB ............................. 4-39 4.6.10 Configuring RFC1583 Compatible External Routing .......................................... 4-39 4.6.11 Configuring the Network Management of OSPF................................................. 4-40

4.7 Maintaining OSPF............................................................................................................ 4-41 4.7.1 Displaying OSPF................................................................................................... 4-41 4.7.2 Resetting OSPF .................................................................................................... 4-42 4.7.3 Debugging OSPF .................................................................................................. 4-42

4.8 Examples for Configuring OSPF...................................................................................... 4-42 4.8.1 Configuring OSPF Basic Functions....................................................................... 4-43 4.8.2 Example for Configuring OSPF Stub Areas.......................................................... 4-48 4.8.3 Configuring OSPF NSSA Areas............................................................................ 4-53 4.8.4 Configuring DR Election of OSPF......................................................................... 4-57 4.8.5 Example for Configuring OSPF Virtual Links ........................................................ 4-63

4.9 Troubleshooting ............................................................................................................... 4-66 4.9.1 OSPF Neighbors Cannot be Established.............................................................. 4-66 4.9.2 Incorrect OSPF Routing Information..................................................................... 4-67

Operation Manual - IP Routing Volume Quidway NetEngine20 Series Routers Chapter 4 OSPF Configuration


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Note:

Chapter 4 OSPF Configuration

4.1 Introduction

Open Shortest Path First (OSPF) is a link state-based interior gateway protocol (IGP) developed by the IETF. At present, OSPF version 2 (defined in RFC2328) is used for IPv4.

Hereinafter the term OSPF, mentioned in this document, refers to OSPFv2, unless otherwise stated.

SPF features: ations: It supports networks in various sizes and can support up to

transmits the update packets as soon as the network

ree: It calculates routes with the shortest path tree algorithm according to

rtition: It allows the network of AS to be divided into different areas for

multiple equal-cost routes to the same

rchy: There are four possible types of paths used to route traffic to

ket authentication to

supports multicast address to

O Wide applic

hundreds of routers. Fast convergence: Ittopology changes. This synchronizes the change in the Autonomous System (AS). Loop-fthe collected link states. This ensures that the algorithm itself generates no loop routes. Area pathe convenience of management. This further abstracts the routing information transmitted between the areas. This abstraction, in turn, reduces the consumption of network bandwidth. Equal-cost multi-route: It supports destination. Routing hierathe destination. They are listed here in decreasing order of preference, intra-area, inter-area, type 1 external or type 2 external. Authentication: It supports the interface-based pacguarantee the security of the packet interaction. Multicast transmission: On some type of links, itreceive and send packets. This reduces the interference with other devices.



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riginates a Link

he LSAs from other routers, and all these LSAs

e

algorithm to calculate

II. Router ID

To run the OSPF protocol, a router must have a router ID. A 32-bit unsigned integer,

If no router ID is specified by any

III. OSPF

es of packets. They are as follows: local router and is used to

of two routers.

ate Acknowledgment (LSAck) packet: It acknowledges the received

IV. LS s

OSPF encapsulates the descriptions of the routing information in the LSAs and advertises them.

4.1.1 OSPF Basic Concepts

I. Process of OSPF Route Calculation

The process of calculating OSPF routes is as follows: Based on the surrounding network topology, each OSPF router o

State Advertisement (LSA). Then it transmits this LSA to other OSPF routers through the update packets. Each OSPF router collects tcompose the Link State Database (LSDB). LSA describes the network topology around a router; while LSDB describes the network topology of the whole AS. OSPF routers can easily transform the LSDB to a weighted directed map. Thweighted directed map actually reflects the topology architecture of the whole network. Apparently, all the routers get the same maps. According to the directed map, each router uses the SPFthe shortest path tree with itself as the root. The tree shows the routes to each node in the AS.

router ID identifies a router uniquely in an AS.

The router ID can be configured manually. command, the system automatically assigns a router ID from the IP addresses on the current interfaces. The largest IP address in Loopback addresses is taken as the router ID. If no Loopback interface is configured, the largest IP address configured on the interface is selected as the router ID.

Packets

OSPF uses five typ Hello packet: It is periodically sent to the peer of a

discover and maintain OSPF neighbor relationship. Database Description (DD) packet: It describes the summary information of the

local LSDB. It is used to synchronize the databases Link State Request (LSR) packet: It requests for the needed LSAs from the

peers. Link State Update (LSU) packet: It transmits the required LSAs to the peers.

Link StLSAs.

A Type



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re the types of commonly used LSAs: Router LSA (Type 1): originated by each router. It describes the link state and

(Type 2): originated by the DR. It describes the link state of the a single area only.

V. Nei

After utside through OSPF interfaces. packets checks some parameters defined in the

both of them are consistent, the neighbor relationship

4.1.2 OSP

I.

a massive network run OSPF, and the routers increase with the unceasing expansion of the network scale. This may lead to a large LSDB,

ory, complicates the operating of SPF algorithm and aggravates the burden of CPU.

ion also brings about an increase in the probability for structural changes in the topology. So the network usually confronts with “turbulence”. A great

g AS into different areas. Areas are

The following a

cost of the router, and is flooded throughout a single area only. Network LSA

local network segment, and is flooded throughout Network Summary LSA (Type 3): originated by the ABR. It describes the routes

of a certain network segment, and is flooded to other areas. ASBR Summary LSA (Type 4): originated by the ABR. It describ es the routes to ASBR, and is flooded to related areas.

AS External LSA (Type 5): originated by the ASBR. It describes the AS external routes, and is flooded to all areas except Stub areas and NSSA areas that will be introduced later. NSSA LSA (Type 7): originated by the ASBR. It describes the AS external routes, and is only transmitted in NSSA areas.

ghbor and Adjacency

In OSPF, the concepts of neighbors and adjacencies are completely different.

an OSPF router starts, it sends Hello packets oThe OSPF router receiving these packets. If the parameters of can be established.

The neighbor relationship between the peers is not equivalent to the adjacency relationship. The relationship depends on the network type. A true adjacency relationship can be established only when two routers can exchange the DD packets and the LSA successfully.

F Areas and Route Aggregation

Area Partition

Suppose that all routers in

which occupies a great amount of mem

Network expans

number of OSPF packets are transmitted on the network and the bandwidth utility of the network is reduced accordingly. Besides, each change in topology structure requires all the network routers to rerun the route calculation.

OSPF addresses the above puzzle by dividinlogically divided router groups, and each area is identified uniquely by an area ID. At the border of an area resides a router rather than a link. A network segment (or a link)



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can only belong to one area, namely, each interface running OSPF must specify explicitly to which area it belongs, as shown in Figure 4-1.

Area3

Area0

Area1

Area2

Area4

Figure 4-1 OSPF area partition

After area partition, you can perform route aggregation on the border routers to reduce the LSAs advertised to other areas. Route aggregation can also minimize the influences caused by the topology changes.

II. Router Types

ng four categories according to their locations in AS, as show in Figure 4-2.

e OSPF area.

2) Area Border Routers (ABR)

ng to two or more areas simultaneously, but one of the areas

connect to the backbone area physically or logically.

backbone area. Thus, ABRs an re backbone routers.

PF g information, it becomes an ASBR.

The OSPF routers fall into the followi

1) Internal routers

All interfaces of these routers belong to a sam

These routers can belomust be a backbone area. An ABR is used to connect the backbone area and the non-backbone areas. It can

3) Backbone routers

These routers have at least one interface that belongs to theall d the routers inside Area0 a

4) AS boundary routers (ASBR)

The routers exchanging routing information with other ASs are ASBRs. ASBR is not necessarily on the AS border. It can be an internal router or an ABR. Once an OSrouter imports some external routin



4-5

Area3

Area0

Area1

Area2

Area4

ASBRIS-IS

Internal Router Backbone Router

ABR

Figure 4-2 OSPF router types

III. Backbone Area and Virtual Link

After area partition, not all the areas are equal. Among them, an area is having area area. The backbone area is responsible for the routes

between areas. The routing information between the non-backbone areas must be forwarded through backbone areas. For this, OSPF defines two rules:

ntain the connectivity with the backbone area.

ABRs are configured at

not connect directly with the backbone area. However, you

ID 0 is called the backbone

All non-backbone areas must mai The backbone area must maintain its own connectivity

However, in practical applications, the physical connectivity cannot be ensured due to the network topology restriction. An OSPF virtual link can be configured to solve this problem.

Virtual link refers to a logical channel established between two ABRs through a non-backbone area. The channel takes effect only after the the two ends of the channel. The area providing a non-backbone area internal route for both the ends of the virtual link is called the transit area.

In Figure 4-3, Area 2 does can configure a virtual link on ABRs to make Area 2 maintain its connectivity with the backbone area.

Virtual LinkABRArea0 Area2ABR

Transit Area

Area1

Figure 4-3 Schematic diagram 1 of the virtual link



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ks, the physically Figure 4-4.

The virtual link also provides the backup links. With the backup linseparated areas can still maintain the logical connectivity, as shown in

VLink

Transit AreaArea1

ABR ABR

Area0

Figure 4-4 Schematic diagram 2 of the virtual link

The virtual link is similar to a point-to-point connection between two ABRs. Thus, like the physical interfaces, the interfaces on this link can be configured with parameters such as the interval of sending Hello packets.

OSPF packets are transmitted directly between two ABRs. The OSPF routers between the ABRs are only responsible for packet forwarding. As the destination addresses of the packets are not that of the OSPF routers, these packets are transparent to them and are forwarded n IP packets.

IV

Configuring a stub area is optional. All areas do not confirm to the configuration

rs in the

Note the following items while configuring a stub area:

command.

rough the stub area.

as commo

. Stub Area

A stub area is a special area in which the ABRs do not propagate the learned AS external routes. In these areas, the size of the routing table of the routers and the routing traffic are significantly reduced.

requirements. Generally, a stub area is a non-backbone area with only one ABR and it is located at the AS boundaries.

To ensure that the route to a destination outside the AS is still reachable, the ABR in an area originates a default route and advertises it to the non-ABR routearea.

The backbone area cannot be configured to be the stub area. If you want to configure an area to be a stub area, all the routers in this area

should be configured with the stub ASBR cannot exist in the stub area. In other words, AS external routes are not

transmitted in the stub area. The virtual link cannot pass th



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V

area (NSSA area) and a new LSA (NSSA LSA or Type-7 LSA) are added in the RFC1587 NSSA option.

stub area in many ways. t imports Type-7

pe-7 LSA

As shown in Figure 4-5, the AS running OSPF includes three areas, Area 1, Area 2 e other two ASs run RIP. The Area 1 is configured as the NSSA area.

Type5 LSA and is transmitted to Area0 and Area 2.

Type-5 LSA will not reach Area 1.

. NSSA Area

A new

As NSSA area is derived from the stub area, it resembles the NSSA does not import AS-External-LSA (namely Type-5 LSA) buLSA.

Ty originates from the ASBR in the NSSA area and spreads inside the NSSA. When Type-7 LSA reaches ABR of NSSA, ABR will transform Type-7 LSA into AS-External-LSA and spread it to the other areas.

and Area0. ThArea 1 transmits the received RIP routes to NSSA ASBR, and then NSSA ASBR originates Type7 LSA and transmits it within Area 1. When Type7 LSA reaches NSSA ABR, it is transformed to

On the other hand, the RIP routes of the AS running RIP in Area 2 are transmitted in OSPF AS by Type-5 LSA originated by ASBR in Area 2. Because Area 1 is an NSSA area,

Similar to the stub area, an NSSA area cannot be configured with virtual links.

Area0 Area1Area2

Type5 Type5

Type5Type5 Type7ASBR ASBRABR ABR

RIP RIP

NSSA Area

Figure 4-5 NSSA area

VI. Route

the same prefix and only advertise one

three routes are aggregated into one route 19.1.0.0/16, Router A only originates onedvertises it to other routers in Area0.

Aggregation

ABR can aggregate the routes with aggregated route to other areas. This is route aggregation.

After area partition, route aggregation can reduce the routing information between the areas. Thus the size of the routing table can be reduced and the calculation speed of the router can be improved.

For example, in Figure 4-6, there are three intra-area routes in Area 19, 19.1.1.0/24, 19.1.2.0/24 and 19.1.3.0/24. If route aggregation is configured on Router A and the

aggregated LSA and a



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Area0

Area19

19.1.0.0/16ABR ABR

19.1.1.0/2419.1.2.0/219.1.3

4.0/24

....

RouterC RouterA

RouterB

Figure 4-6 Route aggregation

OSPF has two types of aggregation: 1) ABR aggregation

When an ABR transmits routing information to other areas, it origiper network segment. If some continuous segmentsaggregate these segments into a single segment using the abr-suIn this way, ABR only sends an aggregated LSA. Any LSA falling iaggregation network segment of this command is not transmitted seaccordingly reduces the LSDB scale in other areas.

nates Type-3 LSA exist in this area, you can

mmary command. nto the specified

parately. This

Once the aggregate segment of a certain network is added to the area, all the sses are not broadcasted separately to other areas.

aggregate segment. The routing information of the entire aggregate network segment is broadcast.

n is configured, if the local router is ASBR, it will aggregate

V

AS internal network structure. The external route

imported AS external routes into Type 1 and Type 2.

internal routes of the IP addreThese IP address are in the range of the

2) ASBR aggregation

After the route aggregatiothe imported Type5 LSA. This LSA is within the aggregate address range. After the NSSA area is configured, it will aggregate the imported Type7 LSA within the aggregate address range.

If the local router is ABR, it will aggregate Type5 LSA transformed from Type7 LSA.

II. Route Types

The OSPF uses four types of routes listed below in the descending order of precedence:

Intra area route Inter area route Type 1 external route Type 2 external route

By default, the protocol precedence of the first two routes is 10, and that of the last two routes is 150.

The first two routes describe the describes how to select a route to the destination outside the AS. OSPF divides the



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utes refer to the received IGP routes such as RIP routes and static route. Because of their relatively high reliability, the calculated cost of the external

routes. In other words, the cost of a Type-1 external route equals the t h the corresponding ASBR plus the cost for ASBR to reach

e r to the received EGP routes. Because of their relatively considered greater than the cost of any path internal to

ral equal-cost Type 2 routes exist, the internal distance to the

4.1.3 OSP

I.

ast Multi-access (NBMA): If the link layer protocol is Frame Relay,

lsorily. The common practice is to change a non-fully connected NBMA into a P2MP network. The protocol packets in this network are

cast mode (224.0.0.5). the link layer protocol is PPP, HDLC or LAPB, OSPF

protocol packets in this network are ast mode (224.0.0.5).

II

The and orks.

routeyou of its adjacent routers and their

The mus

Type 1 external ro

routes is the same as that of the routes inside the AS, and is comparable with the cost of OSPFcos for the router to reacthe destination.

Typ 2 external routes refelow reliability, Type-2 cost isAS. Thus, the cost of a Type-2 external route equals the cost for ASBR to reach the destination. When seveASBR is used to break the tie.

F Network Types

Four Network Types

OSPF divides networks into four types by link layer protocol: Broadcast: If the link layer protocol is Ethernet or FDD, OSPF defaults the

network type to broadcast. The protocol packets in this network are transmitted in multicast mode (224.0.0.5 and 224.0.0.6).

Non-BroadcATM or X.25, OSPF defaults the network type to NBMA. The protocol packets in this network are transmitted in unicast mode.

Point-to-Multipoint (P2MP): No matter what the link layer protocol is, OSPF does not default the network type to P2MP. A P2MP network must be changed from other network types compu

transmitted in multiPoint-to-point (P2P): Ifdefaults network type to P2P. Thetransmitted in multic

. Configuration Principles for NBMA Networks

NBMA network refers to a non-broadcast and multi-accessible network. ATM Frame Relay networks are typical NBMA netw

You need to make some special configurations for the NBMA networks. Its adjacent rs cannot be discovered by broadcasting Hello packets. So for this interface, must manually configure the IP addresses

election rights.

NBMA network must be fully connected, namely, any two routers in the network t be directly reachable. If not all the routers are directly accessible on an NBMA



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netwpeer interface type to P2P.

a P2MP network is unnecessarily

An NBMA network needs to elect DR and BDR; while a P2MP network has no

etwork must be changed

hile P2MP transmits packets by multicast.

II

ssions which s. Designated

infor

If a D lid due to some fault, it must be re-elected and synchronized. It e

up this process, OSPF puts forward the concept of Backup Designated Router R

In faadja the routers on the

the B ded and the adjacencies n established, the process is very fast. The electing of a new BDR

takes a long time but it does not exert any influence on the route calculation.

d

ork, you can configure the interface type to P2MP. If the router has only one on the NBMA network, you can change the

The differences between NBMA and P2MP networks are as follows: In OSPF, an NBMA network refers to a network that is fully connected, non-broadcast and multi-accessible; whilefully connected.

DR and BDR. NBMA is a default network type. A P2MP n

compulsorily from other networks types. The common practice is to change a non-fully connected NBMA network into a P2MP network.

NBMA transmits packets by unicast and neighbors need to be configured manually; w

I. DR and BDR

In broadcast and NBMA networks, routing information is transmitted between any two routers. If there are n routers in the network, n X (n-1)/2 adjacencies need to be established. In this case, the route changes result in multiple transmiare unnecessary. It also wastes the precious bandwidth resourceRouter (DR) is defined in the OSPF to solve this problem. All the routers send

mation only to the DR for broadcasting the network link states to the network.

R becomes invatak s a long time and meanwhile the route calculation becomes incorrect. To speed

(BD ).

ct, BDR is a backup for DR. DR and BDR are elected in the mean time. The cencies are also established between the BDR and all

segment. They also exchange the routing information. When the DR becomes invalid, DR becomes DR instantly. Since no re-election is nee

have already bee

Adjacencies are not established between two routers other than DRs or BDRs (called as DR Others), nor does the DR Others exchange any routing information. Thus, it reduces the number of adjacencies between any two routers in broadcast or NBMA networks.

In Figure 4-7, the real line represents Ethernet physical connections, and the dash line represents the established adjacencies. Only seven adjacencies are needeamong five routers with the DR/BDR mechanism as shown below.



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DR BDR

DR Other DR Other DR Other

Figure 4-7 Schematic diagram of DR and BDR

IV

etwork segment. r the DR/BDR election.

eater than 0 are the eligible

ted DR in the packet and sends rs self-proclaimed to be

If two routers have the same ed as the DR. A router, whose

NBMA type, it is necessary to elect DR.

A router acts as a DR on a certain network segment, in the sense of router DR on one interface, but can be a BDR or DR

Other on the other interface.

the BDR is not necessarily the router with the second highest priority.

4.1.4 OSPF Packet Format

. Election Process for DR/BDR

DR is not designated manually. It is elected by all the routers in the nThe DR priority of an interface determines its qualification foIn the network segment, routers with priorities gr"candidates".

Votes are the hello packets. Each router puts the elecit to all the other routers on the segment. Among all the routethe DR, the one with the highest priority will be elected. priority, the one with the larger router ID will be electpriority is 0, cannot be elected as a DR or BDR.

Note the following: Only when an interface is of broadcast or

A p2mp or a p2p interface need not elect DR.

interface. Maybe a router is a

If a new router is added after DR and BDR election, it is impossible for the router to become the DR even if it has the highest priority.

The DR on the network is not necessarily the router with the highest priority. Likewise,

OSPF directly encapsulates its protocol packets into IP packets, using IP protocol 89. Figure 4-8 shows a relatively complete OSPF packet (take LSU packets as an example):



4-12

OSPF PacketHeader

Number ofLSAs LSA HeaderIP Header LSA Data

Figure 4-8

I. OSP

OSPF has five types of packets, which all have the same packet header, as shown in

OSPF packet format

F Packet Header

Figure 4-9.

Authentication

0 7 15 31

Version Packet lengthType

Router ID

Area ID

AuTypeChecksum

Figure 4-9 OSPF packet header format

The main fields are explained as follows:

SPF packet type. It ranges from 1 to 5, corresponding to Hello packet,

Note:

Version: OSPF version number. For OSFPv2, it is 2. Type: O

DD packet, LSR packet, LSU packet and LSAck packet respectively. Packet length: total length of the OSPF packet (including the packet header). Its

unit is byte. AuType: authentication type. It can be 0, 1 and 2, corresponding to no

authentication, simple authentication and MD5 authentication respectively. Authentication: Its value depends on “AuType”. When “AuType” is 0, it is not

defined. When “AuType” is 1, it is the password information. When “AuType” is 2, it contains Key ID, MD5 authentication data length and the sequence number.

The MD5 authentication data is added behind the OSPF packet and is not included hin t e Authentication field.



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II l

Hello l r. It contains the values of timers, DR, BDR and the known neighbors. Figure shows the Hello packet format.

. He lo Packet

packet is commonly used. It is periodically sent to the neighbors of the locaroute4-10

Authentication

7 15 310

Version Packet lengthType=1

Router ID

Area ID

Checksum AuType

...

HelloInterval

RouterDeadInterval

Rtr PriOptions

Network Mask

Designated Router

Backup Designated Router

Neighbor

Figure 4-10 Hello packet format

The main fields are explained as follows: Network Mask: the mask of the network to which the interface sending Hello

packets belongs. HelloInterval: the interval of sending Hello packets. If the intervals of two

adjacent routers are different, the neighbor relationship cannot be established. Rtr Pri: DR priority. If it is set to 0, this router cannot be DR/BDR. RouterDeadInterval: Invalid time. If no Hello packet is received from the

neighbor during this time, the neighbor is considered as invalid. If the invalid time of two adjacent routers is different, the neighbor relationship cannot b

III. DD Packet

their own LSDBs. It contains the header of an LSA, which can uniquely identify the

of an

Figure 4-11 shows the DD packet format.

eestablished.

When two routers synchronize their databases, they use DD packets to describe

LSA. This reduces the traffic size transmitted between the routers, since the header LSA only occupies a small portion of the overall LSA traffic. With the header,

the peer router can judge whether it already has the LSA.



4-14

0 7 15 31


Router ID

Area ID

Checksum AuType

Authentication

Interface MTU Options 00000 I

LSA Headers ...

M MS

DD Sequence Number

Figure 4-11 DD packet format

e

s

router ID is Master. When “MS” is 1, it indicates the sender is Master. d by Master, it increases by 1 when a DD

packet is transmitted. The Slave confirms with the sequence number of the re the reliability and completeness of the nce number.

IV. LS

route

pack

The main fields are explained as follows: Interface MTU: The maximum length of IP packet transmitted from this interfac

without fragmentation. I (Initial): When multiple DD packets are transmitted continuously, if it is the first

DD packet, the “I” is set to 1; otherwise, the “I” is set to 0. M (More): When multiple DD packets are transmitted continuously, if it is the last

DD packet, the “M” is set to 0; otherwise, the “M” is set to 1, which indicatethere are other DD packets followed.

MS (Master/Slave): When two OSPF routers exchange DD packets, themaster/slave relationship should be confirmed first. The one with a greater

DD Sequence Number: Prescribe

Master. The Master and Slave ensutransmitted DD packets by the seque

R Packet

After two routers exchange DD packets, the one knows it lacks which LSA of the peer r. At this time, it will send LSR packets to the peer to request LSA needed. The

LSR packet contains the summary of the requested LSA. Figure 4-12 shows the LSR et format.



4-15

0 7 15 31

Authentication

Version Type=3 Packet length

Router ID

Area ID

AuTypeChecksum

......

LS type

Link State ID

Advertising Router

Figure 4-12 LSR packet format

The main fields are explained as follows: LS type: LSA type. For example, Type1 indicates Router LSA. Link State ID: the field of the LSA header. It depends on “LS type”. Advertising Router: the router ID of the router originating this LSA.

V. LSU Packet

It is used to transmit the required LSAs tomultiple LSAs (complete content

the peer router. It contains a collection of s). Figure 4-13 shows the LSU packet format.

Authentication

310 7 15


Router ID

Area ID

Checksum AuType

Number of LSAs

LSAs...

Figure 4-13 LSU packet format

VI. LSAck Packet

It acknowledges the received LSU packets. It contains the Header (s) of LSA(s) to be acknowledged (an LSAck packet can acknowledge multiple LSAs). Figure 4-14 shows its packet format.



4-16

Authentication

0 7 15 31

Version

Router ID

Area ID

Packet length

AuTypeChecksum

LSA Headers...

Type=5

Figure 4-14 LSAck packet format

VII. LSA Header Format

same packet header, as shown in Figure 4-15. All LSAs have the

0 7 15 31

LS age

Link State ID

Options LS type

Advertising Router

LS sequence number

LS checksum length

Figure 4-15 LSA header format

The main fields are explained as follows: LS age: the time during which LSA lasts after it is originated. Its unit is second.

No matter LSA is transmitted on the links or saved in LSDB, its value increases continuously.

Link State ID: the value is determined by the type of LSA. r: the sequence number of LSA. Other routers determine

which LSA is the newest based on this value. f bytes.

LS type: the type of LSA.

LS sequence numbe

length: total length of LSA (including LSA Header) in the unit o

VIII. Router LSA

Figure 4-16 shows Router LSA format.



4-17

310 7 15

LS age

Link State ID

Options LS type=1

Advertising Router

LS sequence number

LS checksum length

0 # linksEV B 0

Link ID

Link Data

Type # TOS metric

......

TOS 0 TOS metric

Link ID

......

Link Data

Figure 4-16 Router LSA format

The main fields are explained as follows: Link State ID: indicates the router ID of the router originating this LSA at first. V (Virtual Link): If the router originating this LSA is one end of the virtual link, this

“V” is set to 1. E (External): If the router originating this LSA is ASBR, this “E” is set to 1. B (Border): If the router originating this LSA is ABR, this “B” is set to 1. #links: It indicates the number of links described in LSA, and includes all links

and interfaces in some area where the router resides.

IX. Network LSA

It is originated by the DR in broadcast or NBMA networks. LSA records the router IDs rk.

Figure 4-17 shows Network LSA format.

of all the routers on this netwo



4-18

7 15 310

LS age

Link State ID

Options LS type=2

Advertising Router

LS sequence number

LS checksum length

Network Mask

Attached Router

......

Figure 4-17 Network LSA format

The main fields are explained as follows: Link State ID: the interface address of the DR. Network Mask: The address masks of the broadcast or NBMA networks. Attached Router: the router IDs of all the routers (including DRs) connected on

X. Summary

have the same format.

0 15 31

the same network.

LSA

Originated by ABR, both the Type3 and Type4 LSAs

Figure 4-18 shows Summary LSA format.

7

LS age Options LS type=3 or 4

Link State ID

Advertising Router

LS sequence number

LS checksum length

Network Mask

metric

......

0

TOS metricTOS

Figure 4-18 Summary LSA format

The main fields are explained as follows: Link State ID: For Type3 LSA, it is the advertised network address. For Type4

LSA, it is the router ID of ASBR.

Network Mask: For Type3 LSA, it indicates the network address mask. F r nd is set to 0.0.0.0.

oType4 LSA, it makes no sense a



4-19

n address.

Metric: the route cost to the destinatio

Note:

The Type3 LSA can be used to advertise default routes. In this case, the Link State nd Network Mask are set to 0.0.0.0. ID a

XI. AS-External

es to the destinations outside the AS.

Figure 4-19 shows AS-External LSA format.

15 31

LSA

Originated by ASBR, it describes the rout

0 7

LS age

Link State ID

Options LS type=5

Advertising Router

LS sequence number

LS checksum length

Network Mask

metric

......

0

TOS metricTOS

E

Forwarding address

External Route Tag

Forwarding address

External Route Tag

E

Figure 4-19 AS-External LSA format

The main fields are explained as follows: Link State ID: the advertised destination address of another external AS. Network Mask: the mask of the destination address to be advertised. E (External Metric): the type of the external metric. For Type2 external route, it is

te, it is set to 0. Metric: the route cost.

ith the advertised destination address are

t use this

set to 1; for Type1 external rou

Forwarding Address: The packets wforwarded to this address.

External Route Tag: the tag added to the external route. OSPF does nofield itself, and it is used to manage external routes.



4-20

X

form 0.

15 31

II. NSSA External LSA

It is originated by ASBR, and can only be transmitted in NSSA areas. It has the same at as that of AS-External LSA, as shown in Figure 4-2

0 7

LS age

Link State ID

Options LS type=7

Advertising Router

LS sequence number

LS checksum length

Network Mask

metric

......

TOS

Forwarding address

E

External Route Tag

Figure 4-20 NSSA External LSA format

4.1.5 OSPF Features Supported by the NE20

I.

OSPF supports multi-process. Many different OSPF processes can run on a same router. These processes are independent. The route interaction between the different

tween the different routing protocols.

An interface of a router can only belong to a certain OSPF process.

sistent (no cation in plain text or MD5 authentication in encrypted text).

n passwords of all routers in a network segment must be

II

Multi-process

OSPF processes is similar to the interaction be

II. Authentication

OSPF supports packet authentication. Only the OSPF packets, which pass the authentication, are received. If the packets do not pass authentication, the normal neighbor relationship is not established.

The authentication types of all routers in one area must be conauthentication, authentiThe authenticatioconsistent.

I. OSPF Supports for IGP Shortcut and Forwarding Adjacency

OSPF supports IGP shortcut and forwarding adjacency. These features allow OSPF to use an LSP as a possible outgoing interface to reach destination. Without this feature, OSPF cannot take the advantage of a LSP even if it exists.



4-21

rding adjacency alone is enabled, OSPF can also use the LSP as a means of reaching destination.

abled can use

The difference between IGP shortcut and forwarding adjacency lies in: If forwa

If IGP shortcut alone is enabled, only the router on which it is enthe LSP in its route.

Note:

For detailed configuration of this feature, refer to Quidway NetEngine20 Series Routers Operation Manual MPLS Volume.

IV

OSPF sup orts multi-instance, which can run between PEs and CEs in VPN

erent ASs. In this way, the OSPF routes ed in one site are transmitted to another site as external routes. This causes a

fic and some avoidable network management problems.

configure domain ID on PE to differentiate the VPNs where different sites reside. Thus, different sites in one VPN see each other as

directly connected thorough a leased line. This leads to better network

. OSPF Support for VPN

pnetworks.

In BGP MPLS VPN, many sites of one VPN can use OSPF as its internal routing protocol. However, they are handled as difflearnheavy OSPF traf

In the NE20 implementation, you can

if connected directly. Thus, the PE routers exchange OSPF routing information as if they were management and effective OSPF usage.

Note: For detailed configuration of this feature, refer to Quidway NetEngine20 Series Routers Operation Manual VPN Volume.

V. OSPF Sham Links

OSPF Sham Links are unnumbered point-to-point links between two PE routers over an MPLS VPN backbone network.

e BGP extended community attributes carry the route information over

to originate Type 3 summary link state advertisement from PE to CE. These routes are considered as inter-area routes.

wever, if a router connects to PE routers in its own area and establishes an intra-area route (backdoor route) to a particular destination, the VPN traffic always

In general, ththe MPLS VPN backbone between BGP peers. This information can be used by OSPF running on PE at the other end

Ho



4-22

ather than the backbone route. This is because the OSPF intra area routes established in the routing table have relatively higher priorities. To

ra area path with a lower cost to the PE router.

traverses the backdoor r

avoid this anomaly, an unnumbered point-to-point sham link is configured between the PE routers. This provides an int

Note: For related configurations of OSPF sham links, refer to Quidway NetEngine20 Series Routers Operation Manual VPN Volume.

ocols and Specifications

The protocols and specifications related to OSPF are:RFC2328: OSPF Version 2

4.1.6 Prot

4.2 Configuring OSPF Basic Functions

4.2.1 Esta

I.

efore configuring other related OSPF functions, you must enable OSPF and specify the interface and area ID.

nabled, you can configure OSPF commands in interface view. With OSPF disabled, the related commands configured in interface

Before configuring OSPF, you need to complete the following tasks: Configuring the link layer protocol

ses of the interfaces to keep the network layers of the adjacent nodes reachable

blishing the Configuration Task

Applicable Environments

B

No matter whether OSPF is e

view remain unchanged.

II. Preconfigured Tasks

Configuring the network layer addres

III. Data Preparations

To configure OSPF, you need the following data.

No. Data

1 Router ID

2 OSPF process ID

3 Areas which each interface belongs to respectively



4-23

ures IV. Configuration Proced

No. Procedure

1 Enabling OSPF and entering O SPF view

2 Configuring the network segments included by each area

4.2.2 Enabling OSPF and Entering OSPF View

Step Action Command

1 Enter system view. system-view

2 Enable OSPF and enter . ospf [ process-id ] [ router-id router-id ]

enter ospf [ process-id ] [ vpn-instance ] [ router-id router-id ]

OSPF view

3 Enable OSPF and OSPF view of the VPN instance. vpn-instance-name

To ensure the stability of OSPF, you should determine the division of router IDs and manually configure them while planning the network. When configuring router ID manually, you should ensure the router IDs of any two routers in a single AS are d rent. nsistent with the IP address of a c ain in the IP address of an interface on the router.

hen multiple OSPF processes are enabled on a router, it is necessary to specify different process IDs. OSPF process ID is a local conce fect on its packet exc other routers. T refor n also exc , even with different process ID

The NE2 PF multi-instance, and you can configure OSPF to run in VPN in nce cified nstance. Otherwis l instanc

iffe Generally, the router ID is configured coert terface of this router. A common practice is to set the router ID to be

The NE20 supports OSPF multi-processes. W

pt, with no ef hange with he e, different routers ca hange packetss.

0 supports OSsta . If the VPN instance is spe

e, it belongs to the globa, the OSPF process belongs to that ie.

Note: The process ID of OSPF (including OSPF multi-instance) is unique. That is, the process IDs of OSPF multi-instance cannot be the same with the process IDs configured previously.



4-24

4.2.3 Configuring the Network Segments Included by Each Area

Step Action Command


2 Enter OSPF view. ospf [ process-id ]

3 Enter OSPF area view. area area-id

4 Configure the network segments included by the areas.

network ip-address wildcard-mask

A network segment can only belong to one area, namely, each interface running OSPF must specify to which area it belongs.

Most configurations should be based on the area. Wrong configuration may disable formation transmission between the neighboring routers, and even lead to

congestion or self-loop of the routing information.

4.3 Configuring OSPF Area Features

4.3.1 Establishing th

I. Applicable Environmen

Af SPF e nsib SAs, you can e some non-backbone areas on the AS border as stub area.

tub areas cannot import external routes, thus leading to the concept of NSSA area. In NSSA area, Type7 LSA transmission is allowed. Originated by ASBR in NSSA

.

ne area, and the backbone area should maintain its own connectivity.

However, in practical applications, the physical connectivity cannot be ensured due to the network topology restrictions. OSPF virtual link can be configured to solve this problem.

The following deals with the configuration procedures of the features mentioned above.


Before configuring OSPF area features, you need to complete the following tasks:

in

e Configuration Task

ts

ter area pxte

artition, the number of LSAs in the network dility is enhanced. To reduce its rouconfigur

ecreases and the Oting table size and the number of L

S

area, Type7 LSA is transformed to AS-External LSA when it reaches the ABR of NSSA, and is further advertised to other areas

After area partition, the OSPF routes between non-backbone areas are updated with the help of the backbone area. OSPF stipulates that all the non-backbone areas should maintain the connectivity with the backbo



4-25

f the interfaces to keep the network layers of the adjacent nodes reachable Configuring OSPF basic features


need the following data.

Configuring the network layer addresses o

To configure OSPF areas, you

No. Data

1 Type of the area

2 Interfaces included in the area

3 The default routes advertised to the area

. Configuration Procedures IV

No. Procedure

1 Configuring OSPF stub areas

2 Configuring OSPF NSSA areas

3 Configuring OSPF virtual links

4.3.2 Configuring OSPF Stub Areas

I. ring a Router as a Stub Router ConfiguStep Action Command



3 Configure a router as a stub router. stub-router

Note: When all the interfaces of a router are in one stub are

configured as a stub router. a, this router should be

n configuring a stub router connecte BR, you need to configure the

Whe d with Astub command in area view.



4-26

s II. Configuring OSPF Stub Area

Step Action Command



area area-id

4 Configure the current area as a stub area.

stub [ no-summary ]

e default default-cost cost

3 Enter OSPF area view.

5 Configure the cost of throutes to the stub area.

This command in step 5 is configured on ABRs.

Not e: When co d to configure the stub comman

nfiguring a stub router connected with ABR, you need in area view.

4.3.3 Configuring OSPF NSSA Areas

Step Action Command

1 system-view Enter system view.



SA area. nssa [ default-route-advertise ] [ no-import-route ] [ no-summar

f the default rea. cost

4 Configure an area as a NS

y ]

5 Configure the cost oroutes to the NSSA a default-cost

All the routers conn area mu nssa comman

ected to the NSSAd.

st be configured with the



4-27

4.3.4 Con SPF Virtual Links figuring O

Step Action Command




nd configure it.

vlink-peer router-id [ hello seconds] [ retransmit seconds ] [ trans-delay seconds ] [ dead sec ple [ plain | cipher ] password mac-md5 } key-id er ] password ] | authentic

4 Create a virtual link a

onds] [ [ sim] | [ { md5 | h

[ plain | ciphation-null ]

Y should configure this command at the other e

4.4 Configuring OSPF Network Types

4.4.1 Establishing the Configuration Task

I. Applicable Environments

st be fully connected, any two routers in the network are directly irement cannot be satisfied, and you need to ommands.

F MA networks, if there are no directly reachable en some two routers, y interface ty the router in NBMA networks only has one peer, you can change the interface type to P2P.

In addition, when configuring broadcast rks or NBMA networks, you can s cify t h interf the DR/BDR election in the network.DR or BD


Before configuring OSPF network types, he following tasks: Configuring the network layer addresses of the interfaces to keep the network


To configure OSPF network types, you need the following data.

ou nd of the virtual link.

OSPF divides networks into four types by the link layer protocol. Because an NBMA network mureachable. In most cases, this requchange the network type forcibly by c

or NB links betweou can configure the pe to P2MP. If

netwope he DR priorities of eac ace to affect

In general, the routers with highR.

performance and reliability are elected as

you need to complete t

layers of the adjacent nodes reachable Configuring OSPF basic functions



4-28

No. Data

1 Network types to be used

2 IP addresses of the neighbors (for NBMA networks)

3 DR priorities of the interfaces

IV. Configuration Procedures

No. Procedure

1 Configuring network types of OSPF interfaces

2 Configuring neighbors for NBMA networks

3 Configuring DR priorities of OSPF interfaces

4.4.2 Configuring Network Types of OSPF Interfaces

Step Action Command


2 Enter interface view. interface interface-type interface-number

OSPF interfaces. p2mp | p2p 3 Configure network types of

ospf network-type { broadcast | nbma |

}

e for the interface, the previous network type lly.

4.4.3 Con

Wh n you configure a new network typeis removed automatica

figuring Neighbors for NBMA Networks

Step Action Command



3 Configure neighbors for NBMA networks. peer ip-address [ dr-priority priority ]

re needed for NBMA networks. Because adjacent ro cannot be discovered by broad packets, you must manually configure interface and their election rights.

Some special configurations auters casting Hello

the IP addresses of its adjacent routers for this



4-29

4.4.4 Configuring DR Priorities of OSPF Interfaces

Step Action Command


2 Enter interf . interface interfa ber

es of y priority

ace view ce-type interface-num

3 Configure DR prioritiOSPF interfaces.

ospf dr-priorit

When configuring broadcast networks or NBMA networks, you can specify the DR riorities of each interface to affect the DR/BDR election in the network.

4.5 Controlling OSPF Routing Information

I. A able Enviro

A r the s section, y the advertising and receiving of OSPF routing inform rt the route rotocols.

II. P econ

Before controlling OSPF routing information, you need to complete the following sks:

III Preparations

owing data.

p


pplic nments

fte configurations in thi ou can control ation, and impo s of other p

r figured Tasks

ta Configuring the network layer addresses of the interfaces to keep the network

layers of the adjacent nodes reachable Configuring OSPF basic functions

. Data

To control OSPF routing information, you need the foll

No. Data

1 Link cost

2 Filtering list if routing informatio ltered

3 of the ro lt

n needs to be fi

Name and process ID uting protocol to be imported and its defauvalue



4-30


No. Procedure

1 Configuring OSPF route aggregation

2 Configuring OSPF to filter the received routes

Filter ABR Type3 LSA

col preference of OSPF

3 Configuring OSPF to

4 Configuring the link cost of OSPF

5 Configuring the maximum number of equal-cost routes

6 Configuring the proto

7 Configuring OSPF to import external routes

4.5.2 Con u

I. n n

fig ring OSPF Route Aggregation

Co figuring ABR Route AggregatioStep Action Command



view. area -id

4 Configure ABR route abr-summary ip-address mask [ advertise cost ]

3 Enter area area

aggregation of OSPF. | not-advertise | cost

his command only takes effect on ABRs.

on

T

II. Configuring ASBR Route Aggregati

Step Action Command



ip-address mask se ] [ tag tag ] [ cost cost ]

3 Configure ASBR route asbr-summaryaggregation of OSPF. [ not-adverti

This command only takes effect on ASBRs.



4-31

d Routes 4.5.3 Configuring OSPF to Filter the Receive

Step Action Command


2 Enter OSP ospf [ process-i

ilter the umber | ip-prefix ort

F view. d ]

3 Configure OSPF to freceived routes.

filter-policy { acl-nip-prefix-name } imp

A ynamadvertised and received LSAs because the routing information is hidden in the link tate.

ou actually filter the routes calculated by OSPF. Only the filtered routes are added into the routing table.

4.5.4 Configuring OSPF to Filter ABR Type3 LSA

d ic routing protocol based on the link state, OSPF does not filter the

s

Using the filter-policy import command, y

Step Action Command


2 Enter OSPF view.

Enter area view.

ospf [ process-id

area area-id

]

3

4 Configure OSPF to filter ABR Type-3 LSA.

filter { acl-number | ip-prefix ip-prefix-name | route-policy route-policy-name } { export

port } | im

4.5.5 Configuring the Link Cost of OSPF

I. C figu PF Interfaon ring the Cost of OS ces Step Action Command



3 Configure the cost of OSPF ospf cost cost interfaces.



4-32

II. Configuring Bandwidth Reference Value

Step Action Command



3 Configure bandwireference value.

dth ference value bandwidth-re

If no cost of the interface is configured ex erface view, OSPF calculates its ost automatically based on the interface bandwidth. The calculation formula is the

interface cost equals the bandwidth reference value divided by interface bandwidth. y changing the bandwidth reference value.

4.5.6 Configuring the Maximum

plicitly in intc

You can change interface cost indirectly b

Number of Equal-Cost Routes

Step Action Command



3 Configure the maximum number of equal-cost routes.

maximum load-balancing number

4.5.7 Co SPF nfiguring the Protocol Preference of O

Step Action Command


2 Enter OSPF view.

Configure the protocol

ospf [ process-id ]

3 preference of OSPF.

preference [ ase ] [ route-policy route-policy-name ] preference

Many dynamic routing protocols may run on one router, leading to sharing and selecting routing information among different routing protocols. The system sets preferences for each routing protocol. When different protocols discover a same route, the route with a higher preference is selected.



4-33

4.5.8 Conf rin rt Externa

I. Configu s of Other Protocols

igu g OSPF to Impo l Routes

ring OSPF to Import RouteStep Action Command



Import routprotocols.

import-route proto ss-id ] [ cost cost ] [ type typ route-policy

me ]

4 Configure to filter the filter-policy { acl-number | ip-prefix ort [ protocol ]

3 es of other col [ procee ] [ tag tag ] [

route-policy-na

imported routes. ip-prefix-name } exp

Step 4 is er a speci specifying e protocol. If the protocol is not specified, OSPF filters all the imported routing

information.

optional. You can filt fic kind of routing information byth

Note: Using the import-route command, you cannot import the default routes of the external routes.

transforms the external routes satisfying the requirements to Type5 LSA and advertises them. OSPF filters the imported routes, namely, OSPF only

II. nfigu rt DefaultCo ring OSPF to Impo Routes

Step Action Command


2 Enter OSPF view.

type type ] [ route-policy route-policy-name ]

ospf [ process-id ]

3 Import default routes to OSPF processes.

default-route-advertise [ summary ][ always ] [ cost cost ] [

You can force OSPF to import a default route with this command.



4-34

Note:

If the default route is imported to the OSPF routing domain and some OSPF router within it is configured with static default route, you need to set the precedence of

he routing table. static default route lower than that of the imported default route. Otherwise, the default route may not be the one with the highest preference in t

III. Configuring the Related Parameters for OSPF to Import Routes

Step Action Command



3 Configure the default valfor parameters related toimporting routes (co

ues

st, number of routes, tag and type).

number | tag tag | default { cost cost | limit type { 1 | 2 } } *

When OSPF imports external routes, you can configure the default values of some additional parameters, such as cost, number of routes, tag and type. The route tag is

rotocol related information. For example, it is used to differentiate the

4.6 Adju


I. Applicable Environments

eed of the OSPF networks and the network overload caused by protocol packets. On some low s nks, you nee sider the delay of transmittin e interface.

B djus ion interval, in the resource consumption d to fre nges.

In relat cosecurity

OSPF a gement, and you can bind OSPF MIB with a certain p send trap messages and record logs.

to tag the pnumber of ASs when OSPF receives BGP.

sting and Optimizing OSPF Networks

By changing the OSPF packet timer, you can adjust the convergence sp

peed li d to con g LSAs on th

y a ting the SPF calculat you can restraue quent network cha

a ively secure network, you canof OSPF networks.

lso supports network manarocess,

nfigure OSPF authentication to improve the



4-35

II

plete the following

to keep the network layers of the adjacent nodes reachable


To adjust and optimize OSPF networks, you need the following data.

. Preconfigured Tasks

Before adjusting and optimizing OSPF networks, you need to comtasks:

Configuring the network layer addresses of the interfaces

Configuring OSPF basic functions

No. Data

1 Value of the packet timer

2 Authentication type and password


No. Procedure

1 Configuring OSPF packet timer

2 Configuring the delay of transmitting LSU packets on the interface

nterval of SPF calculation

4 Disabling the interface to transmit OSPF packets

7

ber of LSAs in an LSDB

e cost calculation method compatible with that in RFC1583

10 Configuring the network management of OSPF

3 Configuring the i

5 Configuring Stub router

6 Configuring authentication for OSPF

Configuring the MTU in DD packets

8 Configuring the maximum num

9 Configuring th

4.6.2 Conf rin igu g OSPF Packet Timer

Step Action Command



3 Configure the interval of sending hello packets on the

ospf timer hello seconds

interface.



4-36

Step Action Command

4 Configure the interval of ospf timer poll sesending poll packets on thNBMA interface.

e conds

5 Configure the dead time during which the adjacent relationship is invalid.

ospf timer dead seconds

6 Configure the interval of retransmitting LSAs between ospf timer retransmit seconds the adjacent routers.

It is necessary to keep the consistency of the hello timer between OSPF neighbors. is inversely proportional to route convergence

speed and network load.

T e on a at least four times f sending hello p kets.

A r a ro its neighb t from its n emen bor in the retransmi the LSA.

Not

Note that the value of the hello timer

he dead tim same interface is the interval oac

fte uter sends an LSA to or, it waits for the acknowledgement packeeighbor. If no acknowledgssion interval, it will retransmit

t packet is received from its neigh

e: Both hello an rs restore to the default values after the network type is

ng Do no n int unnecessary

retran r than the time for a packet to be transm t

d dead timecha ed.

t set the LSA retransmissio erval too small. Otherwise, smission will be caused. It must be greateitted a round between two rou ers.

4.6.3 Configuring the Delay of Transmitting LSAs on the Interface

Step Action Command



3 Configure the delay of transmitting LSAs on the interface.

ospf trans-delay seconds

Considering that OSPF packet transmission on the link costs some time, you should add some delay time to the age time of LSA before transmission.



4-37

Note:

Pay much attention to this configuration on low speed links.

4.6.4 Configuring the Interval of SPF Calculation

Step Action Command


2 Enter OSPF view. ospf [ process-id

interval seconds

]

3 Configure the interval of SPF calculation. spf-schedule-

Wheneve PF should be recalculated. Calculating the shortest change will consume enormous resources and affect the

peration efficiency of the router.

4.6.5 Disabling the Interface to Transmit OSPF Packets

r the LSDB of OSPF changes, Spath upon

o

Adjusting the SPF calculation interval, however, can restrain the resource consumption due to frequent network changes.

Step Action Command



3 Disable the interface to transmit OSPF packets.

silent-interface { all | interface-type interface-number }

T nt OSPF ro rmation from being acquired by the routers on a certain network, rface com le the interface to transmit OSPF packets.

Different processes can disable the same interface to transmit OSPF packets, but th silen y here the specified process has been enabled, with no effect on the interface of other

rocesses.

tablished on the interface. Thereby, the capability

o preve uting info use the silent-inte mand to disab

e t-interface command is onl valid for the OSPF interface w

p

After an OSPF interface is set to be in silent status, the interface can still advertise its direct route. However, the hello packets of the interface will be blocked, and no neighboring relationship can be es



4-38

for OSPF to adapt to the networking can be enhanced, which will reduce the consumption of system resources.

4.6.6 Configuring Stub Router

Step Action Command



3 Configure Stub router. stub-router

tub router is used to control the traffic. It tells other OSPF routers not to forward The Sdata by using the Stub router, but these routers can have a route to the Stub router.

In Router LSAs generated by the Stub router, you need to set the metric of all links to infinity.

Note: The Stub router is independent of the Stub area.

figuring Authentication for OSPF 4.6.7 Con

Step Action Command



Enter OSPF area view. area area-id

tion -mode { simple | md5 |


mode of the OSPF interface (MD5 authentication).

hmac-md5 } key-id [ plain | cipher ] password

Configure non-authentication mode of the OSPF interface.

ospf authentication-mode null

3

4 Configure authenticamode of OSPF area.

authenticationhmac-md5}

5 Quit to OSPF view. quit

6 Quit to system view. quit

8 Configure authentication mode of the OSPF interface (simple authentication).

ospf authentication-mode simple [ plain | cipher ] password

Configure authentication ospf authentication-mode { md5 |



4-39

the OSPF packets passing the authentication can be received, otherwise, the neighbor relationship cannot be

stablished normally.

The authentication type of all routers in one area must be consistent, and the network segment must be consistent.

4.6.8 Configuring the MTU in DD Packets

OSPF supports packet authentication. Only

e

authentication password of all routers in one

Step Action Command


2 Enter Ethernet interface view. rface-type interface-number

D terface.

interface inte

3 Enable to fill the MTU in Dpackets sent by the in

ospf mtu-enable

The inte ual MTU w command is configured, the interface will fp kets

4.6.9 Configuring the Maximum Nu

rface replaces the act ith 0 when sending DD packets. After thisill the Interface MTU field of the DD

ac with the actual MTU.

mber of External LSAs in LSDB

Step Action Command


2 ospf [ process-id ]

3 Configure the maximum number of external LSAs in

lsdb-overflow-limit number

Enter OSPF view.

LSDB.

4.6.10 Configuring RFC1583 Compatible External Routing

Step Action Command



Configure RFC1583 outing.

rfc1583 compa3 compatible external r

tible

When a s d le LSAs, the routing rule defined i that in RFC1583. After this command is

ame external route is calculaten RFC2328 is different from

according to multip



4-40

4.6.11 Configuring the Network Management of OSPF

I. Configuring OSPF MIB Binding

configure, the rule in RFC2328 can be compatible with the routing rule defined in RFC1583

Step Action Command


2 Configure OSPF MIB binding. ospf mib-binding process-id

When multiple OSPF processes are enabled, you can configure OSPF MIB to select e process under processing, namely, to which process the OSPF MIB is bound. th

II. Configuring OSPF TRAP

Step Action Command


2 Enable OSPF TRAP. enable ospf | ifcfgerror |

ifstatechange | w | lsdboverflow |

maxagelsa | nbrstatechange | originatelsa | txretransmit | vifauthfail | vifcfgerror | virifrxbadpkt |

snmp-agent trap[ process-id ] [ ifauthfailifrxbadpkt | lsdbapproachoverflo

virifstatechange | viriftxretransmit | virnbrstatechange ]

OSPF can be configured to forward diversified SNMP TRAP packets and a certain OSPF process can be specified through process ID to send SNMP TRAP packets.

PF TRAP configuration is valid for all OSPF processes.

III. Configuring OSPF Log

If the process-id is not specified during configuration, OS

Step Action Command



3 Enable log information. enable log [ config | state | error ]



4-41

4.7 Ma

4.7.1 Displaying

Af cute tthe running of the OSPF configuration, a n.

Table 4-1 Displaying the running of OSP

intaining OSPF

OSPF

ter the above configurations, exe he display command in any view to display nd to verify the effect of the configuratio

F

Action Command

View the brief information of the OSPF routing process. d ] brief display ospf [ process-i

View OSPF statistics. display ospf [ process-id ] cumulative

View LSDB information of OSPF.

self-originate ] } ]

display ospf [ process-id ] lsdb [ { brief | [ { router | network | summary | asbr | nssa | opaque-link | opaque-area | opaque-as } link-state-id ] [ originate-router advertising-router-id |

View OSPF neighbor information. display ospf [ process-id ] peer [ interface-type interface-number ] [ neighbor-id ]

View OSPF next hop information. displa process-id ] nexthop y ospf [

View OSPF routing table.

displa ss-id ] routing -type

nexth

y ospf [ proce[ interface interfaceinterface-number ] [ nexthop

op-address ]

View OSPF virtual links. display ospf [ process-id ] vlink

View OSPF request list. display ospf [ process-id ] request-queue [ interface-type interface-number ] [neighbor-id ]

View OSPF retransmission list. display ospf [ process-id ] retrans-queue [ interface-type interface-number ] [ neighbor-id ]

View the information of OSPF ABR and ASBR. display ospf [ process-id ] abr-asbr

View OSPF interface information. disinterface-t

play ospf [ process-id ] interface [ all | ype interface-number ]

View OSPF er display ospf [p rror rors. rocess-id ] e

View OSPF asbr-summary. ummary [ ip-address mask ] display ospf [ process-id ] asbr-s



4-42

4.7.2 Resetting OSPF

Execute the reset command in user view

T

to reset OSPF counters or connections.

able 4-2 Resetting OSPF

Action Command

Reset OSPF counters. reset ospf counters [ neighbor[ interface-type interface-number ] [ router-id ] ]

Restart OSPF processes. reset ospf [ process-id ] process [ graceful-restart ]

Clear the routes imported by OSPF. reset ospf redistribution

4.7.3 Debu

E mmand in us

Table 4-3 Debugging OSPF

gging OSPF

xecute the debugging co er view to debug OSPF.

Action Command

Enable the debugging of OSPF packet.

debugging o pf [ process-id ] packet [ ack mp |

s| dd | hello | request | update | rcv-dusnd-dump ] [ filter { src | nbr } { acl-number | ip-prefix ip-prefix-name } ]

Enable the debugging of OSPF hot-standby. debugging ospf [ process-id ] hot-standby

Enable the debugging of OSPF event. debugging ospf [ process-id ] event

Enable the debugging of OSPF LSA packet.

debugging ospf [ process-id ] lsa-originate

Enable OSPF SPF debugging.

debugging ospf [ process-id ] spf { all | brief | intra }

debugging ospf [ process-id ] spf

nssa } [ filter { acl acl-number | ip-prefix ip-prefix-name } ]

{ asbr-summary | ase | net-summary |

4.8 Exam uring OS

ples for Config PF



4-43

Note:

In te this section, only the commands rela d to OSPF configuration are listed.

4.8.1 Configuring OSPF Basic Functions

I. Networking Requirements

routers run OSPF, and the whole AS is partitioned into three areas. Ro d Router B serve as ABRs to f utes between areas.

A er shousegments.

II.

As shown in Figure 4-21, all uter A an orward the ro

fter the configuration, each rout ld learn the routes from AS to all network

Networking Diagram

RouterA POS1/0/0RouterB

POS1/0/068.0.2/24

RouterD

192.168.0.1/24 192.1

2.1/24

Area0

POS2/0/0192.168.1.1/24

POS2/0/0192.168.

POS2/0/0192.168.2.2/24

Eth3/0/0172.17.1.1/24

RouterC POS2/0/0192.168.1.2/24

Area1

Eth3/0/0172.16.1.1/24

Area2

Networking diagram of OSPF basic configurations

II1) Configuring IP addresses of the interfaces (omitted)

) Configuring OSPF

# Configure Router A.

[RouterA] ospf

[RouterA-ospf-1] area 0

[RouterA-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[RouterA-ospf-1-area-0.0.0.0] quit


Figure 4-21

I. Configuration Procedures

2



4-44

k 192.168.1.0 0.0.0.255


quit

spf-1-area-0.0.0.2] network 192.168.2.0 0.0.0.255

[RouterB-ospf-1-area-0.0.0.2] quit

3) Verifying the configuration

[RouterA] display ospf peer

OSPF Process 1 with Router ID 192.168.0.1

ace 192.168.0.1(Pos1/0/0)'s neighbors

.168.2.1 Address: 192.168.0.2 GR State: Normal

is Master Priority: 1

15:04

bors

[RouterA-ospf-1-area-0.0.0.1] networ

# Configure Router B.

[RouterB] ospf

[RouterB-ospf-1] area 0

[RouterB-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[RouterB-ospf-1-area-0.0.0.0]


[RouterB-o

# Configure Router C.

[RouterC] ospf

[RouterC-ospf-1] area 1

[RouterC-ospf-1-area-0.0.0.1] network 192.168.1.0 0.0.0.255

[RouterC-ospf-1-area-0.0.0.1] network 172.16.1.0 0.0.0.255

[RouterC-ospf-1-area-0.0.0.1] quit

# Configure Router D. [RouterD] ospf

[RouterD-ospf-1] area 2

[RouterD-ospf-1-area-0.0.0.0] network 192.168.2.0 0.0.0.255

[RouterD-ospf-1-area-0.0.0.0] network 172.17.1.0 0.0.0.255

[RouterD-ospf-1-area-0.0.0.0] quit

# View OSPF neighbors of Router A.

Neighbors

Area 0.0.0.0 interf

Router ID: 192

State: Full Mode:Nbr

DR: None BDR: None MTU: 0

Dead timer due in 36 sec

Neighbor is up for 00:

Authentication Sequence: [ 0 ]

Neigh



4-45

terface 192.168.1.1(Pos2/0/0)'s neighbors

Address: 192.168.1.2 GR State: Normal

sec

routing information of Router A. uting

Cost Type NextHop AdvRouter Area

92.168.1.2 172.16.1.1 0.0.0.1

1 0.0.0.0

1 0.0.0.1

192.168.0.2 192.168.2.1 0.0.0.0

Stub 192.168.0.1 192.168.0.1 0.0.0.0

: 0 NSSA: 0

# View LSDB of Router A. [RouterA] display ospf lsdb


Type LinkState ID AdvRouter Age Len Sequence Metric

Router 192.168.2.1 192.168.2.1 874 48 80000006 1562

48 80000005 1562

Sum-Net 192.168.1.0 192.168.0.1 630 28 80000001 1562

72.17.1.0 192.168.2.1 411 28 80000001 1563

Sum-Net 192.168.2.0 192.168.2.1 429 28 80000001 1562

Sum-Net 172.16.1.0 192.168.0.1 565 28 80000001 1563

Area: 0.0.0.1

Area 0.0.0.1 in

Router ID: 172.16.1.1

State: Full Mode:Nbr is Slave Priority: 1

DR: None BDR: None MTU: 0

Dead timer due in 39

Neighbor is up for 00:07:32


# View the OSPF[RouterA] display ospf ro


Routing Tables

Routing for Network

Destination

172.16.1.0/24 1563 Stub 1

172.17.1.0/24 3125 Inter-area 192.168.0.2 192.168.2.

192.168.1.0/24 1562 Stub 192.168.1.1 192.168.0.

192.168.2.0/24 3124 Inter-area

192.168.0.0/24 1562

Total Nets: 5

Intra Area: 3 Inter Area: 2 ASE

Link State Data Base

Area: 0.0.0.0

Router 192.168.0.1 192.168.0.1 976

Sum-Net 1



4-46

er Age Len Sequence Metric

.168.1.2 964 48 80000003 1562

8.0.1 590 48 80000002 1562

1 526 60 80000005 1562

Sum-Net 172.17.1.0 192.168.0.1 410 28 80000001 3125

Sum-Net 192.168.2.0 192.168.0.1 428 28 80000001 3124

30 28 80000001 1562

and test connectivity using the ping command.

[RouterD] display ospf routing


Routing Tables

Routing for Network

Destination Cost Type NextHop AdvRouter Area

172.16.1.0/24 4687 Inter-area 192.168.2.1 192.168.2.1 0.0.0.2

172.17.1.0/24 1 Stub 172.17.1.1 192.168.2.2 0.0.0.2

192.168.1.0/24 4686 Inter-area 192.168.2.1 192.168.2.1 0.0.0.2

192.168.2.0/24 1562 Stub 192.168.2.2 192.168.2.2 0.0.0.2

192.168.0.0/24 3124 Inter-area 192.168.2.1 192.168.2.1 0.0.0.2

Total Nets: 5

Intra Area: 2 Inter Area: 3 ASE: 0 NSSA: 0

[RouterD] ping 172.16.1.1

PING 172.16.1.1: 56 data bytes, press CTRL_C to break

Reply from 172.16.1.1: bytes=56 Sequence=1 ttl=253 time=62 ms




--- 172.16.1.1 ping statistics ---

5 packet(s) received

0.00% packet loss

ms

Type LinkState ID AdvRout

Router 192.168.1.2 192

Router 192.168.0.1 192.16

Router 172.16.1.1 172.16.1.

Sum-Net 192.168.0.0 192.168.0.1 6

[RouterA]

# View the routing table of Router D


5 packet(s) transmitted

round-trip min/avg/max = 16/59/94

[RouterD]



4-47

IV

1) Configuration file of Router A #

sysname RouterA

#

interface Pos1/0/0

link-protocol ppp

ip address 192.168.0.1 255.255.255.0

ink-protocol ppp

pf 1

terface Pos1/0/0

pf 1

255

0.0.0.255

turn

n file of Router C #

sysname RouterC

. Configuration Files

#

interface Pos2/0/0

l

ip address 192.168.1.1 255.255.255.0

#

os

area 0.0.0.0

network 192.168.0.0 0.0.0.255

area 0.0.0.1

network 192.168.1.0 0.0.0.255

#

return

2) Configuration file of Router B #

sysname RouterB

#

in

link-protocol ppp

ip address 192.168.0.2 255.255.255.0

#

interface Pos2/0/0

link-protocol ppp

ip address 192.168.2.1 255.255.255.0

#

os

area 0.0.0.0

network 192.168.0.0 0.0.0.

area 0.0.0.2

network 192.168.2.0

#

re

3) Configuratio



4-48

#

interface Pos2/0/0

link-protocol ppp

ip address 192.168.1.2 255.255.255.0

#

ospf 1

area 0.0.0.1

network 192.168.1.0 0.0.0.255

network 172.16.1.0 0.0.0.255

#

return

4) Configuration file of Router D #

sysname RouterD

#

interface Ethernet3/0/0

ip address 172.17.1.1 255.255.255.0

link-protocol ppp

ip address 192.168.2.2 255.255.255.0

#

ospf 1

area 0.0.0.2

network 192.168.2.0 0.0.0.255

network 172.17.1.0 0.0.0.255

#

return

4.8.2 Example for Configuring OSPF Stub Areas

I. Net

re 4-22, all routers run OSPF, and the whole AS is divided into three as ABRs to forward the routes between areas.

uter D serves as ASBR to import external routes (static routes).

rements is to configure Area 1 as stub area, thus reducing the LSAs t on the route reachability.

#


ip address 172.16.1.1 255.255.255.0

#

interface Pos2/0/0

working Requirements

As shown in Figuareas. Router A and Router B serve Ro

The requiadvertised to this area with no effec



4-49

II. tworking Diagram Ne

RouterA RouterB

RouterD

POS1/0/0192.168.0.1/24

POS1/0/0192.168.0.2/24

POS2/0/0192.168.2.1/24

POS2/0/0192.168.2.2/24

Area0

POS2/0/0192.168.1.1/24

Eth3/0/0172.17.1.1/24

POS2/0/068.1.2/24

Area1

Eth3/0/0

Area2

ASBR

RouterC 172.16.1.1/24

192.1

Stub

g OSPF stub areas

III. Configuration ces (omitted)

Configuring OSPF (same as the previous example) port static routes

tatic 200.0.0.0 8 null 0

uterD-ospf-1] import-route static

quit

er C.

F Process 1 with Router ID 172.16.1.1

Routing Table to ABR and ASBR

Type Destination Area Cost Nexthop RtType

0.0.0.1 1562 192.168.1.1 ABR

Inter-area 172.17.1.1 0.0.0.1 4686 192.168.1.1 ASBR

Routing Tables

Figure 4-22 Configurin

Procedures 1) Configuring IP addresses of the interfa2) 3) Configuring Router D to im[RouterD] ip route-s

[RouterD] ospf

[Ro

[RouterD-ospf-1]

# View ABR/ASBR information on Rout

[RouterC] display ospf abr-asbr

OSP

Intra-area 192.168.0.1

# View OSPF routing table of Router C.

[RouterC] display ospf routing




4-50

1

0.1 0.0.0.1

1

0.1 0.0.0.1

0.1 0.0.0.1

er

.1

er

0

Routing for Network


172.16.1.0/24 1 Stub 172.16.1.1 172.16.1.1 0.0.0.

172.17.1.0/24 4687 Inter-area 192.168.1.1 192.168.

192.168.1.0/24 1562 Stub 192.168.1.2 172.16.1.1 0.0.0.

192.168.2.0/24 4686 Inter-area 192.168.1.1 192.168.

192.168.0.0/24 3124 Inter-area 192.168.1.1 192.168.

Routing for ASEs

Destination Cost Type Tag NextHop AdvRout

200.0.0.0/8 10 Type2 1 192.168.1.1 172.17.1

Routing for NSSAs

Destination Cost Type Tag NextHop AdvRout

Total Nets: 6

Intra Area: 2 Inter Area: 3 ASE: 1 NSSA:

Note:

Wh n Router C is in a common area, there are AS-exte ernal routes in the routing table.

4) Configuring Area 1 as a stub area

b

outerA-ospf-1-area-0.0.0.0] quit

outerC-ospf-1] stub-router

# View the routing table of Router C.



[RouterA] ospf


[RouterA-ospf-1-area-0.0.0.1] stu

[R


[RouterC] ospf

[R


[RouterC-ospf-1-area-0.0.0.1] stub



Routing Tables



4-51

st Type NextHop AdvRouter Area

.0.1

Routing for Network

Destination Co

0.0.0.0/0 65536 Inter-area 192.168.1.1 192.168.0.1 0.0

172.16.1.0/24 1 Stub 172.16.1.1 172.16.1.1 0.0.0.1

172.17.1.0/24 68660 Inter-area 192.168.1.1 192.168.0.1 0.0.0.1

192.168.1.0/24 1562 Stub 192.168.1.2 172.16.1.1 0.0.0.1

192.168.2.0/24 68659 Inter-area 192.168.1.1 192.168.0.1 0.0.0.1

192.168.0.0/24 67097 Inter-area 192.168.1.1 192.168.0.1 0.0.0.1

Total Nets: 6


Note:

After the area where Router C resides is configured as a stub area, the AS-external utes are invisible. Instead, there is a default route. ro

# Configure to disable to advertise Type3 LSA to the stub area. spf

rA-ospf-1-area-0.0.0.0] quit

View OSPF routing table of Router C.

1 with Router ID 172.16.1.1

Routing Tables

AdvRouter Area

63 Inter-area 192.168.1.1 192.168.0.1 0.0.0.1

1 Stub 172.16.1.1 172.16.1.1 0.0.0.1

192.168.1.2 172.16.1.1 0.0.0.1

0

[RouterA] o


[RouterA-ospf-1-area-0.0.0.1] stub no-summary

[Route

#


OSPF Process

Routing for Network

Destination Cost Type NextHop

0.0.0.0/0 15

172.16.1.0/24

192.168.1.0/24 1562 Stub

Total Nets: 3

Intra Area: 2 Inter Area: 1 ASE: 0 NSSA:



4-52

Note:

After the advertisement of Summary LSA to the stub area is disabled, the route entries of the stub router are further reduced, and only the default route to a destination outside the AS is reserved.

IV. Configuration

Configuration file of Router A

interface Pos1/0/0

col ppp

interface Pos2/0/0

link-protocol ppp

ip address 192.168.1.1 255.255.255.0

stub no-summary

#

return

Note:

Files

1) #

sysname RouterA

#

link-proto

ip address 192.168.0.1 255.255.255.0

#

#

ospf 1

area 0.0.0.0

network 192.168.0.0 0.0.0.255

area 0.0.0.1

network 192.168.1.0 0.0.0.255

The configuration file of Router B is the same as that in the previous example, and is omitted here.

2) Configuration file of Router C


ip address 172.16.1.1 255.255.255.0

#

#

sysname RouterC

#



4-53

link-protocol ppp

stub-router

area 0.0.0.1

0.0.0.255

0.0.0.255

Configuration file of Router D

erface Ethernet3/0/0

.1 255.255.255.0

nk-protocol ppp

ess 192.168.2.2 255.255.255.0

.0 0.0.0.255

etwork 172.17.1.0 0.0.0.255

route-static 200.0.0.0 8 NULL0

#

4.8.3 Configuring OSPF NSSA Areas

I. Netw

hown in Figure 4-23, all routers run OSPF, and the whole AS is divided into three r B serve as ABRs to forward the routes between areas.

uter D serves as ASBR to import external routes (static routes).

interface Pos2/0/0

ip address 192.168.1.2 255.255.255.0

#

ospf 1

network 192.168.1.0

network 172.16.1.0

stub

#

return

3) #

sysname RouterD

#

int

ip address 172.17.1

#

interface Pos2/0/0

li

ip addr

#

ospf 1

import-route static

area 0.0.0.2

network 192.168.2

n

#

ip

return

orking Requirements

As sareas. Router A and RouteRo



4-54

configure Area 1 as NSSA area and configure Router C as nal routes (static routes), and the routing information can be

II. king Diagram

The requirements is toASBR to import extertransmitted correctly inside the AS.

Networ

RouterA POS1/0/0Area0

RouterB

RouterD

POS1/0/0168.0.2/24

POS2/0/0192.168.2.1/24

POS2/0/0192.168.2.2/24

POS2/0/0192.168.1.1/24

Eth3/0/0172.17.1.1/24outerC

192.168.1.2/24

172.16.1.1/24

Area2

192.168.0.1/24 192.

R

POS2/0/0

Area1

Eth3/0/0

ASBRA

NSSA

SBR

g OSPF NSSA areas

III. Configuration Procedures figuring IP addresses of the interfaces (omitted)

the same as the previous example) Router D to import static routes (the same as the previous example)

area

area 1

nssa default-route-advertise no-summary

quit



1] nssa


Figure 4-23 Configurin

1) Con2) Configuring OSPF (3) Configuring4) Configuring Area 1 as an NSSA


[RouterA] ospf

[RouterA-ospf-1]

[RouterA-ospf-1-area-0.0.0.1]

[RouterA-ospf-1-area-0.0.0.0]

[RouterC] ospf

[RouterC-ospf-1-area-0.0.0.



4-55

Note:

It is recommended that the ABR (refers to Router A here) be configured with the default-route-advertise no-summary parameter, thus reducing the size of the

router. Other NSSA routers only need to be configured with the nssa command. routing table of the NSSA

# View OSPF routing table of Router C. [RouterC] display ospf routing


Routing Tables

Routing for Network


0.0.0.0/0 1563 Inter-area 192.168.1.1 192.168.

172.16.1.0/24 1 Stub 172.16.1.1 172.16.1.1 0.0.0.

192.168.1.0/24 1562 Stub 192.168.1.2 172.16.1.1 0.0.0.

0.1 0.0.0.1

1

1


t

ting table of Router D.

routing

ID 172.17.1.1

ng Tables

Routing for Network


172.16.1.0/24 4687 Inter-area 192.168.2.1 192.168.0.2 0.0.0.2

172.17.1.0/24 1 Stub 172.17.1.1 172.17.1.1 0.0.0.2

192.168.1.0/24 4686 Inter-area 192.168.2.1 192.168.0.2 0.0.0.2

192.168.2.0/24 1562 Stub 192.168.2.2 172.17.1.1 0.0.0.2

192.168.0.0/24 3124 Inter-area 192.168.2.1 192.168.0.2 0.0.0.2

Total Nets: 3

[RouterC]

5) Configuring Router C to import static routes [RouterC] ip route-static 100.0.0.0 8 null 0

[RouterC] ospf

[RouterC-ospf-1] import-route static

[RouterC-ospf-1] qui

# View OSPF rou

[RouterD-ospf-1]dis ospf

OSPF Process 1 with Router

Routi



4-56

Destination Cost Type Tag NextHop AdvRouter

Destination Cost Type Tag NextHop AdvRouter

1 NSSA: 0

Note:

Routing for ASEs

100.0.0.0/8 10 Type2 1 192.168.2.1

192.168.0.1

Routing for NSSAs

Total Nets: 6

Intra Area: 2 Inter Area: 3 ASE:

[RouterD]

You can see an AS external route imported by the NSSA area on Router D.

IV


sysname RouterA

#

ip address 192.168.0.1 255.255.255.0

#

interface Pos2/0/0

link-protocol ppp

0

pf 1

rea 0.0.0.1

0.0.0.255


interface Pos1/0/0

link-protocol ppp

ip address 192.168.1.1 255.255.255.

#

os

area 0.0.0.0

network 192.168.0.0 0.0.0.255

a

network 192.168.1.0

nssa default-route-advertise no-summary

#

return



4-57

Note:

The configuration files of Router B and Router D are the same as that in the previous example, and are omitted here.

2) Configuration file of Router C #

sysname RouterC

terface Ethernet3/0/0

172.16.1.1 255.255.255.0

interface Pos2/0/0

col ppp

#

spf 1

import-route static

etwork 172.16.1.0 0.0.0.255

0.0.0 8 NULL0

4.8.4 Configuring DR Election of OSPF

I. Networking Requirments

4-24the following figure, with the highest priority 100 in the network, Router R. With the second highest priority, Router C is elected as BDR. The

ter B cannot be elected as DR. The priority of onfigured and its default value is 1.

#

in

ip address

#

link-proto

ip address 192.168.1.2 255.255.255.0

o

area 0.0.0.1

network 192.168.1.0 0.0.0.255

n

nssa

#

ip route-static 100.

#

return

In FigureA is elected as Dpriority of Router B is 0, and so RouRouter D is not c



4-58

II. g Diagram

RouterD

Eth1/0/01001::2/64

Eth1/0/0

Networkin

RouterBRouterA

1001::1/64

Eth1/0/01001::4/64

RouterC

Eth1/0/01001::3/64

Figure 4-24 Configuring DR election of OSPF

IIConfiguring IP addresses of the interfaces (omitted)

bling OSPF

er id 1.1.1.1

A-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255


uterB] interface ethernet 1/0/0

-Ethernet1/0/0] ip address 192.168.1.2 255.255.255.0

outerB-Ethernet1/0/0] ospf dr-priority 0

[RouterB-Ethernet1/0/0] quit

[RouterB] ospf


[RouterC-Ethernet1/0/0] quit

[RouterC] router id 3.3.3.3

[RouterC] ospf



I. Configuration Procedures 1) 2) Ena


[RouterA] rout

[RouterA] ospf


[Router

[Ro

[RouterB

[R

[RouterB] router id 2.2.2.2



[RouterC] interface ethernet 1/0/0

[RouterC-Ethernet1/0/0] ip address 192.168.1.3 255.255.255.0

[RouterC-Ethernet1/0/0] ospf dr-priority 2



4-59

192.168.1.1

168.1.1(Ethernet6/0/0)'s neighbors

State: Normal

R: 192.168.1.3 MTU: 0

32 sec

n Sequence: [ 0 ]

e: Normal

Nbr is Master Priority: 1

DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0

: 192.168.1.4 GR State: Normal

is Master Priority: 1

192.168.1.3 MTU: 0

00:03:53

ospf dr-priority 100

# Configure Router D.

[RouterD] interface ethernet 1/0/0

[RouterD-Ethernet1/0/0] ip address 192.168.1.4 255.255.255.0

[RouterD-Ethernet1/0/0] quit

[RouterD] router id 4.4.4.4

[RouterD] ospf



# View DR/BDR states.

[RouterA] display ospf peer

OSPF Process 1 with Router ID

Neighbors

Area 0.0.0.0 interface 192.

Router ID: 192.168.1.2 Address: 192.168.1.2 GR

S ate: 2-Way Mode:Nbr is Slave Priority: 1 t

DR: 192.168.1.4 BD

Dead timer due in


Authenticatio

Router ID: 192.168.1.3 Address: 192.168.1.3 GR Stat

State: Full Mode:




Router ID: 192.168.1.4 Address

State: Full Mode:Nbr

DR: 192.168.1.4 BDR:


Neighbor is up for


[RouterA]

3) Configuring DR priorities on the interfaces


[RouterA] interface ethernet 1/0/0

[RouterA-Ethernet1/0/0]



4-60

/0] quit

dr-priority 0


ospf dr-priority 2

quit

iew DR/BDR states.


0)'s neighbors

1.1 GR State: Normal

lave Priority: 100

.1.3 MTU: 0



lave Priority: 0

.1.3 MTU: 0



lave Priority: 2

.1.3 MTU: 0


cation Sequence: [ 0 ]

[RouterA-Ethernet1/0


[RouterB] interface ethernet 1/0/0

[RouterB-Ethernet1/0/0] ospf

[RouterB-Ethernet1/0/0] quit

[RouterC] interface ethernet 1/0/0

[RouterC-Ethernet1/0/0]

[RouterC-Ethernet1/0/0]

# V

[RouterD] display ospf peer

Neighbors

Area 0.0.0.0 interface 192.168.1.4(Ethernet6/0/

Router ID: 192.168.1.1 Address: 192.168.

State: Full Mode:Nbr is S

DR: 192.168.1.4 BDR: 192.168





DR: 192.168.1.4 BDR: 192.168





DR: 192.168.1.4 BDR: 192.168


Authenti

[RouterD]



4-61

Note:

The DR priorities configured on the interfaces will not take effect instantly.

4) Restarting OSPF processes (omitted) uration result

1 with Router ID 192.168.1.4

s neighbors

Address: 192.168.1.1 GR State: Normal

State: Full Mode:Nbr is Slave Priority: 100

ress: 192.168.1.2 GR State: Normal

r Priority: 0

DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0

ress: 192.168.1.3 GR State: Normal

Priority: 2

DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0

F Process 1 with Router ID 192.168.1.1

Interfaces

Area: 0.0.0.0

5) Viewing the config

# View OSPF neighbor state.

[RouterD] display ospf peer

OSPF Process

Neighbors

Area 0.0.0.0 interface 192.168.1.4(Ethernet6/0/0)'

Router ID: 192.168.1.1

DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0




Router ID: 192.168.1.2 Add

State: 2-Way Mode:Nbr is Maste




Router ID: 192.168.1.3 Add

State: Full Mode:Nbr is Slave




# View the OSPF interface state.

[RouterA] display ospf interface

OSP



4-62

Type State Cost Pri DR BDR

192.168.1.1 Broadcast DR 1 100 192.168.1.1 192.168.1.3

[RouterB] display ospf interface

192.168.1.2

Address Type State Cost Pri DR BDR

0 192.168.1.1

eighboring

ge LSAs.

they are neither DR nor BDR.

IV

55.255.0

pf 1

ysname RouterB

IP Address

OSPF Process 1 with Router ID

Interfaces

Area: 0.0.0.0

IP

192.168.1.2 Broadcast DROther 1

192.168.1.3

All neighbors are in full state. This indicates that Router A forms nrelationships with all its neighbors. If the neighbor stays “2-Way”, it indicates both of them are not DR or BDR. Thus, they need not to exchan

All other neighbors are DR Others. This indicates that



sysname RouterA

#


ip address 192.168.1.1 255.2

ospf dr-priority 100

#

os

area 0.0.0.0

network 192.168.1.0 0.0.0.255

#

return


s

#


ip address 192.168.1.2 255.255.255.0

ospf dr-priority 0

#

ospf 1

area 0.0.0.0



4-63

turn

terface Ethernet6/0/0

168.1.3 255.255.255.0

rea 0.0.0.0

4) Configuration file of Router D

address 192.168.1.4 255.255.255.0

f 1

urn

4.8.5 Example for Configuring OSPF Virtual Links

I. Networking Requirements

4-25, Area 2 does not connect with the backbone area directly. Area 1 ct Area 2 and Area 0. A virtual link is configured

ween Router A and Router B.

network 192.168.1.0 0.0.0.255

#

re

3) Configuration file of Router C #

sysname RouterC

#

in

ip address 192.

ospf dr-priority 2

#

ospf 1

a

network 192.168.1.0 0.0.0.255

#

return

#

sysname RouterD

#


ip

#

osp

area 0.0.0.0

network 192.168.1.0 0.0.0.255

#

ret

In Figureserves as a Transit Area to connebet



4-64

II. agram Networking Di

RouterA POS1/0/0192.168.1.1/24

RouterBPOS1/0/0192.168.1.2/24

Eth2/0/0172.16.1.1/16

Area0 Area2

Area1

Eth2/0/010.1.1.1/8

Virtual Link

III. Configuration Procedures sses of the interfaces (omitted)

onfigure Router A.

] ospf 1 router-id 1.1.1.1

uterA-ospf-1-area-0.0.0.0] network 10.0.0.0 0.255.255.255

ea-0.0.0.0] quit

uterA-ospf-1] area 1

0.1] network 192.168.1.0 0.0.0.255

ure Router B.

network 192.168.1.0 0.0.0.255

quit


.0 0.0.255.255

[RouterB–ospf-1-area-0.0.0.2] quit

outer A.

[RouterA] display ospf routing

s

Routing for Network


10.0.0.0/8 1562 Stub 10.1.1.1 1.1.1.1 0.0.0.0

192.168.1.0/24 1562 Stub 192.168.1.1 1.1.1.1 0.0.0.1

Figure 4-25 Configuring OSPF virtual links

1) Configuring IP addre2) Configuring OSPF

# C

[RouterA


[Ro

[RouterA-ospf-1-ar

[Ro

[RouterA-ospf-1-area-0.0.


# Config

[RouterB] ospf 1 router-id 2.2.2.2




[RouterB–ospf-1-area-0.0.0.2] network 172.16.0

# View OSPF routing table of R


Routing Table



4-65

Total Nets: 2


Note:

Area 2 does not connect directly to Area 0. Thus, there is no Area 2 routing table of Router A.

route in the

3) Configure the virtual link

[RouterA] ospf

0.0.1] vlink-peer 2.2.2.2

-0.0.0.1] quit

-peer 1.1.1.1

.0.1] quit

ID 1.1.1.1

Tables

Type NextHop AdvRouter Area

0.0.0.0

1.1.1.1 0.0.0.0

92.168.1.1 1.1.1.1 0.0.0.1

IV. Configuration Files



[RouterA-ospf-1-area-0.

[RouterA-ospf-1-area


[RouterB] ospf 1


[RouterB-ospf-1-area-0.0.0.1] vlink

[RouterB-ospf-1-area-0.0

# View OSPF routing table of Router A.

[RouterA] display ospf routing

OSPF Process 1 with Router

Routing

Routing for Network

Destination Cost

172.16.1.1/32 1563 Inter-area 192.168.1.2 2.2.2.2

10.0.0.0/8 1562 Stub 10.1.1.1

192.168.1.0/24 1562 Stub 1

Total Nets: 3



sysname RouterA



4-66

et2/0/0

interface Pos1/0/0

col ppp

ospf 1 router-id 1.1.1.1

area 0.0.0.0

5.255

network 192.168.1.0 0.0.0.255

interface Pos1/0/0

0.0.0.1

0.0.0.255

4.9 Trou

4.9.1 OS t be Established

I.

OSPF neighbors cannot be established.

#

interface Ethern

ip address 10.1.1.1 255.0.0.0

#

link-proto

ip address 192.168.1.1 255.255.255.0

#

network 10.0.0.0 0.255.25

area 0.0.0.1

vlink-peer 2.2.2.2

#

return


sysname RouterB

#


ip address 172.16.1.1 255.255.0.0

#

link-protocol ppp

ip address 192.168.1.2 255.255.255.0

#

ospf 1 router-id 2.2.2.2

area

network 192.168.1.0

vlink-peer 1.1.1.1

area 0.0.0.2

network 172.16.0.0 0.0.255.255

#

return

bleshooting

PF Neighbors Canno

Fault Description



4-67

II. alysis

If both the physical connection and the lower layer protocol are normal, you can check the OSPF parameters configured on the interface and ensure their consistency with that of the neighboring routers. The area ID should be the same, as

ment and the mask. However, in P2P networks or the networks with the virtual links, the network segment and the mask can be different.

network types of the interfaces of two neighboring routers should be the same. orks, the DR priority of at least one interface should be

III. Troubleshooting

An

well as the network seg

TheFor broadcast or NBMA netwgreater than 0.

Step Action

1 View OSPF neighbors using the display ospf peer command.

2 View OSPF interfaces using the display ospf interface command.

3 hysical connection and the lower layer protocol are mand. If the local router cannot ping through the

remote router, there are some faults in the physical connection and the lower .

4 Check OSPF timer to make sure that the dead time on one interface should Hello interval.

ecify neighbors manually using the peer ip-address command.

t or NBMA networks, the DR priority of at least one interface eater than 0.

Check whether both the pcorrect using the ping com

layer protocol

be at least four times the

5 For NBMA networks, you can sp

6 For broadcasshould be gr

4.9.2 Inco ormation

I.

es of other areas.

II.

s in the backbone area should be connected with each other. If one router is d two or more areas, at least one of the areas is the backbone area. The

backbone area cannot be configured as a stub area.

The routers in the stub area cannot receive AS external routes. If one area is configured as a stub area, all routers connected to this area should be configured with the stub command.

rrect OSPF Routing Inf

Fault Description

OSPF cannot discover rout

Analysis

All areaconfigure



4-68

III. Troubleshooting

No. Action

1 View OSPF neighbors using the display ospf peer command.

2 View OSPF interfaces using the display ospf interface command.

DB is complete using the display ospf lsdb command.

configured correctly using the display current-configuration configuration ospf command. If two or more areas

configured with the stub command, at least one of the areas is the backbone area. However, the backbone area cannot be configured with the

3 Check whether the LS

4 Check whether the areas are

are

stub command.

5 All the routers in one stub area need to be configured with the stub command.

6 If the virtual link is configured, you can check whether the neighbors are normal using the display ospf vlink command.

04-chapter4 ospf configuration

Documents

ospf configuration

ospf areas

ospf features

ospf view

ospf network types

ospf route aggregation

ospf stub areas

ospf nssa areas