Determining IP RoutesIntroducing Routing

OutlineOverviewRouting OverviewStatic and Dynamic Route ComparisonStatic Route ConfigurationDefault Route Forwarding ConfigurationStatic Route Configuration VerificationDynamic Routing Protocol OverviewFeatures of Dynamic Routing ProtocolsThe ip classless CommandInterVLAN RoutingSummary

To route, a router needs to do the following:Know the destination addressIdentify the sources from which the router can learnDiscover possible routes to the intended destinationSelect the best routeMaintain and verify routing informationRouter Operations

Routers must learn destinations that are not directly connected.Router Operations (Cont.)

Static RouteUses a route that a network administrator enters into the router manuallyDynamic RouteUses a route that a network routing protocol adjusts automatically for topology or traffic changesIdentifying Static and Dynamic Routes

Static RoutesConfigure unidirectional static routes to and from a stub network to allow communications to occur.

Defines a path to an IP destination network or subnet or host Router(config)# ip route network [mask] {address | interface}[distance] [permanent] Static Route Configuration

Static Route Example

Default RoutesThis route allows the stub network to reach all known networks beyond Router A.

Verifying the Static Route ConfigurationRouter# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static routeGateway of last resort is 0.0.0.0 to network 0.0.0.0 10.0.0.0/8 is subnetted, 1 subnetsC 10.1.1.0 is directly connected, Serial0S* 0.0.0.0/0 is directly connected, Serial0

Routing protocols are used between routers to determine paths and maintain routing tables.After the path is determined, a router can route a routed protocol.What Is a Routing Protocol?

Autonomous Systems: Interior or Exterior Routing Protocols

Classes of Routing Protocols

Classes of Routing ProtocolsDistance vector Routing protocols

The Distance vector protocols find the best path to the destination by judging the Distance to that hop. [ each time a packet goes to a router is known as HOP]

Any route with the Least hops will be the Best route.

Routers pass periodic copies of their routing table to neighboring routers and accumulate distance vectors.Distance Vector Routing Protocols

Routers discover the best path to destinations from each neighbor.Sources of Information and Discovering Routes

Selecting the Best Route with Metrics

Updates proceed step by step from router to router.Maintaining Routing Information

Link state routing protocolsThe protocols which choose SHORTEST PATH to determine the best path for the Destination.These protocols maintain three types of Tables.For directly attached neighbors.For determining the Topology of whole inter-network.Routing table.

Link state routing protocols know more about the Internetwork then any other type of protocol.OSPF is the complete link state protocol.Link state protocols send regular updates about there routing table to all the connected neighbors after a regular interval.

Link state routing protocols.The protocols which use features of both Distance Vector and Link state are known as hybrid protocols. Exa.. EIGRP

ROUTING LOOPSDistance vector routing protocols keep track of any changes that occur in the internetwork by broadcasting the periodic routing table updates out to all Routers connected. This is good for the maintenance of the internetwork but not for the processing of the routers processor. But the routing updates are send after a specific time period.

ROUTING LOOPSSuppose we have the above scenario with 6 networks. And the update period will be 30 seconds.

ROUTING LOOPSIf network 6 fails then router E will send the update to router C because all other router have the route to network six from the router C.Now router C know about the Failure of the Network 6 but all other A,B and D are still don`t know about the failure bcz C didn`t send update to them till now.

So they keep on sending the routing updates to C for the network 6. and they assume that YES they have path for network 6.

ROUTING LOOPSAfter some time when router C will send update to router B.it will stop routing for network 6.

BUT router A & D are still unknown about the failure{not updated} and they send a update to router B that they have still path for network 6.

ROUTING LOOPSThe problem occur when before update to router A & D about the failure the router A send a HELLO update packet to router B & D about the network 6. and router B & D think that network six will be reachable through router A. and they start sending update to all of the router about this update.

Then router A send request for N/W 6 to B & D, D will send to B, B will send to A, and again and again they will repeat the same procedure in a LOOP.

Known as routing loop.

Metrics or Solutions to stop the Routing loopsMaximum HOP CountOne way of solving the loops is to define the maximum hop count RIP permits a hop count of 15 only means if anything that requires 16th hop is deemed as unreachable.Means after a loop of 15 hops the next network will be considered as unreachable

Metrics or Solutions to stop the Routing loops. Cont..In this methodology the routing information cant be sent back to the direction from which it was received

Metrics or Solutions to stop the Routing loops. Cont..It means when the is a change in any internetwork topology a special update is sent to all neighbors immediately so that they can update there routing tables.

Metrics or Solutions to stop the Routing loops. Cont..If there any network will down then corresponding router will start advertising that network as a 16th network or unreachable network.

This will stop all other to send packets for that network

Collision DomainIt is a network segment with multiple hosts in which they all shares the same bandwidth.Exa.. HUBHub is a 1 collision and 1 broadcast domain

Means if two hosts transmits at same time a collision can occur

Broadcast domainThe boundary in which all devices can see and participate in the broadcast sent from the nay node to any node in the network.

Device SpecificationsHUB:- 1 Collision domain 1 Broadcast domainAt a time only one request can travel to all the nodes connected with the hub.And if there is any collision then a single collision can stop whole network

Switch:- 1 Broadcast domain, multiple collision domain, each port is a separate collision domain, multiple unicast domain.A Switch always performs 1st time broadcast when it is power ON and after that it will always use unicast method for data distribution

Device Specifications contiRouter:- each port of a router is a separate collision domain and a broadcast domain.

Bcz any broadcast or any collision in the internetwork will only affects the connected port of the router not to all the interfaces of the router.

A router used to handle all its ports separately.

Administrative Distance: Ranking RoutesIt is used to give the rank to the routing protocols It is an integer from 0-255

It will show the trustworthiness of any routing protocol.

0 means most trusted.

255 means traffic can`t be pass to that route.

Administrative Distance: Ranking RoutesHow the AD is used.

Whenever a router will receive two routing updates At same time then it will check for the AD distance for that updates and save the update with least AD in its routing table.BUT if the both have the same AD then it will follow the routing metrics of protocol that is used for the routing from the side of routing update.Like [hop count/shortest path]

Administrative Distance: Ranking RoutesSource ADConnected 0Static 1RIP 120 IGRP 100EIGRP 90OSPF 110Unknown 255

255 will never be used.

Classfull Routing Overview/ subnetting FLSMClassfull routing protocols do not include the subnet mask with the route advertisement.Within the same network, consistency of the subnet masks is assumed.Summary routes are exchanged between foreign networks.These are examples of classfull routing protocols:RIP version 1 (RIPv1)IGRP

Classless Routing Overview/ Subnetting VLSMClassless routing protocols include the subnet mask with the route advertisement.Classless routing protocols support variable-length subnet mask (VLSM).Summary routes can be manually controlled within the network.These are examples of classless routing protocols:RIP version 2 (RIPv2)EIGRPOSPFIS-IS

Routing Protocol Comparison Chart

SummaryRouting is the process by which items get from one location to another. In networking, a router is the device used to route traffic. Routers can forward packets over static routes or dynamic routes, based on the router configuration. Static routers use a route that a network administrator enters into the router manually. Dynamic routes use a router that a network routing protocol adjusts automatically for topology or traffic changes.Unidirectional static routes must be configured to and from a stub network to allow communications to occur.The ip route command can be used to configure default route forwarding.The show ip route command is used to verify that static routing is properly configured. Static routes are signified in the command output by S.

Summary (Cont.)Dynamic routing protocols determine how updates are conveyed, what knowledge is conveyed, when to convey knowledge, and how to locate recipients of the updates.A routing protocol that has a lower administrative value is more trustworthy than a protocol that has a higher administrative value.There are three classes of routing protocols: distance vector, link-state, and balanced hybrid.The ip classless command can be used to prevent a router from dropping a packet that is destined for an unknown subnetwork of a directly attached network if a default route is configured.

Slide 1 of 2 Purpose: This slide states the chapter objectives.Emphasize: Read or state each objective so that each student has a clear understanding of the chapter objectives.Note: Catalyst switches have different CLIs. The Catalyst 2900xl and the Catalyst 1900 has a Cisco IOS CLI. The Cisco IOS CLI commands available on the 2900xl is different from the 1900. The Catalyst 5000 family has no Cisco IOS CLI, and use the set commands instead. This class only covers the configuration on the Catalyst 1900 switch.Slide 1 of 2Purpose: This figure introduces students to routing. The router must accomplish the items listed in the figure for routing to occur.Emphasize: Path determination occurs at Layer 3, the network layer. The path determination function enables a router to evaluate the available paths to a destination and to establish the best path. Routing services use network topology information when evaluating network paths. This information can be configured by the network administrator (static routes) or collected through dynamic processes (routing protocols) running in the network.Transition: How do you represent the path to the packets destination?

Slide 2 of 2Purpose: This figure explains that routers must learn about paths that are not directly connected. Emphasize: The router already knows about directly connected networks. It must learn about those networks that are not connected. This chapter describes how routers learn about those paths.

Purpose: This figure introduces students to static and dynamic routes.Emphasize: Static knowledge is administered manuallya network administrator enters it into the routers configuration. The administrator must manually update this static route entry whenever an internetwork topology change requires an update. Static knowledge can be privateby default it is not conveyed to other routers as part of an update process. You can, however, configure the router to share this knowledge.Dynamic knowledge works differently. After the network administrator enters configuration commands to start dynamic routing, route knowledge is updated automatically by a routing process. Whenever new topology information is received from the internetwork, routers update neighbors about the route change.

Purpose: This figure describes how a static route operates.Emphasize: For intercommunication, static routes must be configured in both directions. Static routes are often used to route traffic to a stub network or other network where only a single route to that network exists.Purpose: This figure describes the command syntax used to establish an IP static route.Emphasize: A static route allows manual configuration of the routing table. No dynamic changes to this table entry will occur as long as the path is active. Routing updates are not sent on a link that is only defined by a static route; hence, conserving bandwidth.The ip route field descriptions are as follows:networkDestination network or subnetmaskSubnet maskaddressIP address of next-hop routerinterfaceName of the interface to use to get to the destination network Transition: The next figure provides a static route configuration example.Purpose: This figure gives an example of a static route configuration.

Purpose: This figure gives an example of a default route configuration.Emphasize: With an address and subnet mask of 0.0.0.0 0.0.0.0 in the ip route statement, packets for any network not listed in the routing table will be sent to the next hop, 172.16.2.2.

Slide 2 of 6Purpose: This figure shows how the show frame-relay LMI command is used to verify the LMI type used for signaling. Emphasize: Describe the highlighted output to the students.Purpose: This figure introduces students to routing protocols and compares routing protocols to routed protocols.Emphasize: If network 10.120.2.0 wants to know about network 172.16.2.0, it must learn it from its S0 (or possibly S1) interface.Note: The two routing protocols that will be taught in this course are RIP and IGRP. They are both distance vector routing protocols.

Purpose: This figure discusses autonomous systems, IGPs and EGPs.Emphasize: Introduce the interior/exterior distinctions for routing protocols, as follows: Interior routing protocols are used within a single autonomous system Exterior routing protocols are used to communicate between autonomous systems The design criteria for an interior routing protocol require it to find the best path through the network. In other words, the metric and how that metric is used is the most important element in an interior routing protocol.Exterior protocols are used to exchange routing information between networks that do not share a common administration. IP exterior gateway protocols require the following three sets of information before routing can begin: A list of neighbor (or peer) routers or access servers with which to exchange routing informationA list of networks to advertise as directly reachableThe autonomous system number of the local router

Purpose: This figure introduces the three classes of routing protocols.Emphasize: There is no single best routing protocol.Note: Distance vector routing protocol operation is covered in detail later in this course. Link state and hybrid are only briefly explained after the distance vector discussion. Refer students to the ACRC to learn more about link-state and hybrid routing protocols.

Purpose: This figure introduces the three classes of routing protocols.Emphasize: There is no single best routing protocol.Note: Distance vector routing protocol operation is covered in detail later in this course. Link state and hybrid are only briefly explained after the distance vector discussion. Refer students to the ACRC to learn more about link-state and hybrid routing protocols.

Purpose: This figure introduces the distance vector routing algorithm, the first of the classes of routing protocols, and outlines how it operates. Emphasize: Distance vector algorithms do not allow a router to know the exact topology of an internetwork.This information is somewhat analogous to the information found on signs at a highway intersection. A sign points toward a road leading away from the intersection and indicates the distance to the destination. Further down the highway, another sign also points toward the destination, but now the distance to the destination is shorter. As long as each successive point on the path shows that the distance to the destination is successively shorter, the traffic is following the best path.

Layer 3 of 3Emphasize: Layer 3 adds the final entries received some time later that have distances of 2 from routers A and C. Emphasize: How the routing algorithm defines best determines the most important characteristics of each routing algorithm. Hop countSome routing protocols use hop count as their metric. Hop count refers to the number of routers a packet must go through to reach a destination. The lower the hop count, the better the path. Path length is used to indicate the sum of the hops to a destination. As indicated in the figure, RIP uses hop count for its metric.TicksMetric used with Novell IPX to reflect delay. Each tick is 1/18th of a second.CostFactor used by some routing protocols to determine the best path to a destination; the lower the cost, the better the path. Path cost is the sum of the costs associated with each link to a destination.BandwidthAlthough bandwidth is the rating of a links maximum throughput, routing through links with greater bandwidth does not always provide the best routes. For example, if a high-speed link is busy, sending a packet through a slower link might be faster. As indicated in the figure with highlighting, delay and bandwidth comprise the default metric for IGRP.DelayDepends on many factors, including the bandwidth of network links, the length of queues at each router in the path, network congestion on links, and the physical distance to be traveled. A conglomeration of variables that change with internetwork conditions, delay is a common and useful metric. As indicated in the figure with highlighting, delay and bandwidth comprise the default metric for IGRP.LoadDynamic factor can be based on a variety of measures, including CPU use and packets processed per second. Monitoring these parameters on a continual basis can itself be resource intensive.Layer 3 of 3Layer 3 adds router B, which receives the updated routing table from routerA. In turn, router B will perform its own process to update its routing table given this new topology update from router A. Distance vector updates occur step by step. Typically, a router sends updates by multicasting its table on each configured port, but other methods, such as sending the table only to preconfigured neighbors, are employed by some routing algorithms. Multicast is used by the RIP2, OSPF, and EIGRP routing protocols. RIP and IGRP use broadcast.The routing table can be sent routinely and periodically, or whenever a change in the topology is discovered. Updates sent when changes occur are called triggered updates.

5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.5Purpose: This figure introduces administrative distance. Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information. The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.Purpose: This slide discuss the initial configurations on the routers and switches. Note: There is no setup mode on the Catalyst 1900 switch.