basics of dynamic routing

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Basics of Dynamic Routing

Presented by Aaron Jarvis Network Engineer

Agenda

•Introduction to Dynamic Routing

•Choosing the Right Protocol

•Configuring Dynamic Routing

•How the ITaP Production Data Network uses dynamic routing

Introduction to Dynamic Routing

•What is routing?•How data is forwarded between subnets•Network Layer or Layer 3 in the OSI Model•Provides end-to-end reachability

Introduction to Dynamic Routing

•How are routing decisions made?•Forwarded based on the destination IP address•Router builds/maintains a routing table

•Current view of the network•Populated either dynamically or manually

router#show ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.5.40.54 to network 0.0.0.0

69.0.0.0/19 is subnetted, 1 subnetsO E2 69.51.160.0 [110/1] via 192.5.40.54, 6d21h, Port-channel61O E2 199.233.104.0/24 [110/1] via 192.5.40.54, 3w4d, Port-channel61 192.5.40.0/24 is variably subnetted, 19 subnets, 4 masksD 192.5.40.238/32 [90/131328] via 192.31.0.13, 2d16h, Vlan4094 [90/131328] via 192.31.0.113, 2d16h, Vlan4084O IA 192.5.40.225/32 [110/2] via 192.5.40.54, 3w4d, Port-channel61O IA 192.5.40.227/32 [110/4] via 192.5.40.54, 3w4d, Port-channel61C 192.5.40.240/28 is directly connected, Vlan898D 192.5.40.168/29 [90/3072] via 192.31.0.113, 7w0d, Vlan4084 [90/3072] via 192.31.0.13, 7w0d, Vlan4094Snip……

Agenda





Choosing the Right Protocol

•Interior Routing Protocols•Used within an autonomous system•Used within an area of administrative control

•Exterior Routing Protocols•Used between autonomous systems•Used to peer with networks in which you have no administrative control


•Interior Routing Protocols•Static•RIP•OSPF•EIGRP•ISIS

•Exterior Routing Protocols•BGP

NOTE: This is not an exhaustive list of protocols available but merely a list of those commonly used.


•Static Routing•May be suitable on small networks•Administration intensive as changes have to be made on each router•Commonly used for default routing•0.0.0.0/0 Next Hop Router


•Dynamic Routing Protocol Types•Distance Vector•Routing Information Protocol(RIP)•Interior Gateway Routing Protocol(IGRP)•Enhanced Interior Gateway Routing Protocol(EIGRP)

•Link State•Open Shortest Path First(OSPF)•Intermediate System to Intermediate System(ISIS)

•Path Vector•Border Gateway Protocol(BGP)


•Routing Information Protocol(RIP)•RFC 1058(RIPv1), 1988•Classful, no support for VLSM•No support for authentication

•RFC 2453(RIPv2), 1998•Classless, support for CIDR•Support for authentication

•Uses hop count as routing metric•Slow to converge•Not very scalable•Limited to 15 hops


•Interior Gateway Routing Protocol(IGRP)•Invented by Cisco to overcome limitations of RIP•Allows for hop count up to 255•Allows for multiple route metrics•Bandwidth•Delay•Load•MTU•Reliability

•Classful, no support for VLSM


•Enhanced Interior Gateway Routing Protocol(EIGRP)•Replaced IGRP•Maintains a Topology table•Successors, feasible successors

•Allows for multiple route metrics•Classless, support for CIDR•Very fast to converge•Maintains neighbor relationships•Diffusing Update Algorithm(DUAL)•Not as CPU intensive as OSPF


•Open Shortest Path First(OSPF)•RFC 2328(OSPFv2), 1998•Maintains neighbor relationships•Concept of Areas•Different areas can be used to control flooding of routing information

•Classless, supports VLSM•Fast to converge•CPU Intensive Dijkstra Algorithm•Designing can be complicated


•Intermediate System to Intermediate System(ISIS)•RFC 1142, 1990•Dijkstra Algorithm•Mainly used by large service providers•Does not use IP to carry routing information•Uses ISO addresses

•Level Concept•Level 1 or Intra Area•Level 2 or Inter Area•Level 1/2 or Both

•Classless, supports VLSM


•Border Gateway Protocol(BGP)•RFC 4271(BGPv4), 2006•Peers manually defined•Used typically for multi-homing to ISP(s)•Very scalable•Makes decisions based upon AS Path•Lots of policy options•Very granular control

Agenda





Configuring Dynamic Routing

•How to configure dynamic routing?•Choose a protocol that meets your needs•Each vendor has specific commands but should have a configuration guide available to assist•Plan well to ensure a functional network•Create a diagram•Consider high availability technologies•HSRP•VRRP


•Best Practices•Only enable a routing protocol for interfaces you intend on using •If compromised can cause a lot of problems

•Enable authentication(if available)•Use authentication to ensure that the remote routers are valid peers


•Best Practices Cont…•Control Network Advertisements•Only allow networks to be advertised that should be

•Private Address Space•Use only within your organization

•Private AS Numbers•Strip before sending to ISP

Agenda





How the ITaP Production Network Uses Dynamic Routing

•Routing Protocols Used•Interior•EIGRP•OSPF•Static

•Exterior•BGP

How the ITaP Production Network Uses Dynamic Routing

Whiteboard Drawing

Questions?

basics of dynamic routing

Documents

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dynamic routingintroduction

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