1. Extended Interior Gateway Routing Protocol
EIGRP
Extended Interior Gateway Routing Protocol

2. What is EIGRP A link state protocol
Similar to OSPF in scalability (allegedly easier to configure)
Follows IGRP, where it is faster and can scale
Offers multi-protocol support

3. What is EIGRP Hop count of 224
Uses ( /bandwidth)*256 as a metric [simplified]
Each AS (Autonomous System) will manage separate routed networks on the same ‘wire’

4. What is EIGRP IGRP will distribute to EIGRP and Vice Versa
Router IGRP 123
Network
Router EIGRP 123
Network

5. EIGRP Concepts EIGRP maintains three tables: Neighbour table
Topology table
Routing table
Uses Hellos to check router status
Uses a short hold down timer to check router status
Neighbour discovery and recovery
Reliable Transport Protocol
DUAL finite-state machine algorithm
Measures distances (FD/RD)
Has protocol dependant modules (PDMS = extendible)

6. EIGRP maintains three tables
Neighbour table
Contains list of connected routers
Topology table
Keeps a map of the N/W based on:
connected routers,
costs,
feasible distances,
reported distances,
successors
feasible successors
Routing table
Contains results of the above tables

7. EIGRP Neighbour packets
5 EIGRP packet types are:
Hello
Acknowledgment
Update
Query
Reply
EIGRP routers send hellos to the multicast IP address
All data transport is done by RTP which means that we are not dependant on a system protocol which may fail

8. EIGRP Neighbour packets
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9. The topology table is the clever bit
Uses DUAL finite state machine
Looks at the results of the packet types and exchanges between routers
Lowest cost route is feasible distance
Reported distance can be
Equal the feasible distance thus be the successor,
be lower than the FD (time for a DUAL change),
Or higher which means that we have a feasible successor

10. Image copyright Cisco Academy Programme
So how does DUAL do IT!
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11. Configuring EIGRP Router EIGRP 123 Network 172.16.0.0 No auto-summary
EIGRP automatically summarises keeping routing tables compact, this may not be desired, thus

12. Configuring EIGRP Router EIGRP 123 Network 172.16.0.0 No auto-summary
EIGRP automatically summarises keeping routing tables compact, this may not be desired, thus

13. Configuring EIGRP Router EIGRP 123 Network 172.16.0.0 No auto-summary
EIGRP automatically summarises keeping routing tables compact, this may not be desired, thus

14. Configuring EIGRP
router(config-if)# ip summary-address eigrp autonomous-system-number ip-address mask administrative-distance
Interface serial 0/0
ip summary-address eigrp

15. EIGRP Show commands Show ip eigrp neighbors Show ip eigrp topology
Show ip eigrp interfaces

16. NOW DO THE LABS
in the curriculum