EIGRP

EIGRP

1. 1. EIGRP fundamentals

   • 1. Enhanced Interior Gateway Routing Protocol – An advanced link state routing protocol
   • 2. Fast convergence
   • 3. Scalable
   • 4. Load balancing over unequal cost links
   • 5. Classless (VLSM support) – supports the advertisement of networks that use subnet masks other than the default (ie natural) masks
   • 6. Communicates via multicast
   • 7. Was Cisco-proprietary

2. 2. Routing Structures

   • Show ip eigrp neighbors – shows Neighbor table
   • Show ip eigrp interfaces - shows interfaces participating in the eigrp system
   • Show ip eigrp topology - Contains routes to destinations that eigrp is aware of

3. Path selection

   • Diffusing Update Algorithm (DUAL) – A calculation mode made by EIGRP to determine the best loop-free path to a network
   • Feasible Distance – A neighbor’s Advertised Distance to a network plus the distance to reach that neigbor
   • Successor Route – The primary route to a network, based on the route having the lowest FD of all routes in the EIGRP topology table
   • Feasible Successor Route – A backup route to a network, based on the route having the second lowest Feasible Distance in the EIGRP topology table. (The Feasibility Condition must be met)
     • Before a route can become a Feasible Successor Route, its AD has to be lower than the FD of the Successor route

4. 3. Metric calculation

   • Bandwidth (weakest link)
   • Delay (cumulative)
   • Reliability
   • Load (most load)
   • MTU
   • Big Dogs Really Like Me

5. EIGRP Configuration IPv4

   • R1(config)#router eigrp 100 (autonomous system) must match on all routers R1(config-router)#network 172.16.1.0 0.0.0.3 R1(config-router)#network 10.1.1.0 0.0.0.255 R1(config-router)#network 1.1.1.1 0.0.0.0 R2(config)#router eigrp 100 Do same as R1
   • R3(config)#router eigrp 100 Do same as R2 and R1

6. 4. EIGRP Configuration IPv6

   • R1(config)#ipv6 router eigrp 1 R1(config-rtr)#router-id 1.1.1.1 R1(config-rtr)#int lo0 R1(config-if)#ipv6 eigrp 1 Do for the rest of the interfaces and routers, different router ID
   • R2#show ipv6 route
   • R2#show ipv6 eigrp topology
   • R2#show ipv6 eigrp int
   • R2#show ipv6 protocols

7. 5. Influencing Metric Calculation

   • R1(config)#router eigrp 100 R1(config-router)#metric weights 0 1(k1) 1(k2) 1(k3) 0(k4) 0(k5)

8. 6. Configuring Neighbor Authentication

   • R1(config)#key chain DEMO R1(config-keychain)#key 1 R1(config-keychain)key-string $3creT R1(config-keychain)#int fa 0/1 R1(config-int)#ip authentication key-chain eigrp 100 DEMO md5 Do same thing on other router R1#show key chain

9. 7. Configuring Unequal Cost Load Balancing

   • R2(config)#router eigrp 100 R2(config-router)#variance 6 (makes two paths in the routing table)

10. 8. Auto Summarization Option

    • R2(config)#router eigrp 100 R2(config-router)#no auto-summary

11. 9. The Passive Interface Option

    • R2(config)#router eigrp 100 R2(config-router)#passive-interface fa 0/0 (must not make passive if you want to make neighborship)