Advanced Routing Protocols

CCNA Guide to Cisco Networking

Chapter 9 : Advanced Routing Protocols

Objectives

• Describe classful and classless routing protocols

• Describe and configure RIPv2

• Describe and configure EIGRP

• Describe and configure OSPF

• Control routing traffic

Classful And Classless Routing Protocols

• How the routing protocols handles subnets masks information

• Classful routing protocols– RIPv1– IGRP– Major network boundaries (Class A, B, or C)– Don not carry subnet mask information– Cannot use or work with

• Discontiguous subnets • VLSM

Classful And Classless Routing Protocols (continued)







• Classless routing protocols– RIPv2– EIGRP– OSPF– BGP– Not restricted to Major network boundaries – Carry subnet mask information– Work with






Routing Information Protocol Version 2

• Metric – Hops– Max 15 hops

• 16th hop unreachable

• Carry subnet mask information

• Updates are multicast 224.0.0.9

• Ability to authenticate routing peers

Routing Information Protocol Version 2 (continued)






• RIPv2 authentication steps– Define a key chain– Define keys in the key chain– Enable authentication on the interface by

specifying the key chain to be used– Enable either clear text or MD5 authentication– Manage the keys (optional key lifetimes)




Enhanced Interior Gateway Routing Protocol

• Cisco proprietary protocol– Hybrid protocol– Features both distance-vector and link-state protocols

• Classless– Not restricted to Major network boundaries – Carry subnet mask information– Work with


• Route IP, IPX, and AppleTalk– Protocol Dependent Modules (PDMs)

Enhanced Interior Gateway Routing Protocol (continued)

• Routing updates are– Non-periodic– Partial– Bounded

• Authentication of peers

• Backwards compatible with IGRP

• Automatically share or redistribute between IGRP and EIGRP


• EIGRP components– Protocol Dependent Modules– Neighbor discovery and maintenance– Reliable Transport Protocol– Diffusing Update Algorithm (DUAL)

• Hello packets– Multicast packets to 224.0.0.10

• Every 5 seconds on T1 or greater links

– Unicast packets• Every 60 seconds on less than T1 speeds


• Hello packets (continued)– Hold-down timer is 3 times Hello interval– Peer routers do not need to have same settings– Timers are configurable on a per-interface basis– Hello packets use the Reliable Transport Protocol

(RTP)• EIGRP uses 5 packets types

– Hellos– Acknowledgements– Updates– Queries– Replies



• Diffusing Update Algorithm (DUAL) key terms– Successor– Feasible distance (FD)– Reported distance (RD)– Feasible successor– Feasible condition– Adjacency

• EIGRP tables– Neighbor table– Topology table– Routing table







EIGRP Configuration

EIGRP Configuration (continued)


• EIGRP peer routing authentication steps– Define a key chain– Define keys in the key chain– Enable authentication on the interface by

specifying the key chain to be used– Manage the keys (optional key lifetimes)


Open Shortest Path First

• OSPF– Open standard– Link-state routing protocol– Classless routing and VLSM– Authentication of routing peers– Share a common view of the entire network– Sends out link-state advertisements (LSA)

• LSAs are not periodic• Sent only when a change occurs

Open Shortest Path First (continued)

• Suited for large networks

• High CPU and memory demands

• OSPF creates the following– Adjacency database– Topology database– Touting table



• OSPF Concepts– Link– Link-state– Area– Cost– Adjacencies database– Topological database– Designated router

• Router election with router ID

– Backup designated router




OSPF Operation

• OPSP operation– First: Form adjacencies with neighbors– Second: Election of DR and BDR– Third: Flood LSAs – Fourth: Select best routes

• Dijkstra’s Shortest Path Algorithm– Loop-free – Best cost path– CPU and Memory demands

OSPF Operation (continued)

Single-Area OSFP Configuration

Single-Area OSFP Configuration (continued)

Controlling Route Traffic

• “passive-interface” command

• RIP will receive updates not send– RouterD(config)# router rip– RouterD(config-router)# passive-interface s0

• EIGRP and OSPF will not send or receive updates

Controlling Route Traffic (continued)

Summary

• Large, complex internetworks using variable length subnet masks require routing protocols that can handle the task

• Several advanced routing protocols are in common use on networks today

• These protocols are classless and carry subnet mask information in their routing table updates

Summary (continued)

• RIPv2 is a classless routing protocol built as an extension to RIPv1

• It supports modern networks’ use of VLSM and authentication

• In addition, it provides backward compatibility with RIPv1 when configured correctly

• Still, RIPv2 suffers from all the pitfalls of distance-vector routing protocols

Summary (continued)

• EIGRP is a Cisco proprietary protocol designed to incorporate some of the features of link-state routing protocols

• It is, however, still a distance-vector routing protocol• EIGRP does support classless routing• Its use of neighbor, topological, and routing tables allows

for quick convergence in the event of a link failure• In fact, for each destination network, EIGRP keeps a

successor or best route, and if possible a feasible successor or backup route

Summary (continued)

• The open standards protocol OSPF is the link-state protocol of choice in many networks; it supports VLSM, classless routing, and fast convergence

• In OSPF, each router uses the Shortest Path First Algorithm to determine the best loop-free path to each network

• Each router also uses an adjacency table, topological table, and routing table to pick the best route to a destination

Documents

Advanced Routing Protocols