![](https://alyxmandario.com/wp-content/uploads/2021/05/eigrp-1024x576.jpg)
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers.
Troubleshooting Guide
- Mismatch Autonomous System number.
- Mismatch Authentication (key string)
- Mismatch metric value (K Values)
- Passive interface
- Check for filtered routes (ACL, Distribution list)
EIGRP Metric
![](https://alyxmandario.com/wp-content/uploads/2021/05/metric.jpg)
By default, only bandwidth and delay are used as Eigrp metrics.
Use delay if we want to influence network traffic rather than bandwidth.
EIGRP Topology Table
![](https://alyxmandario.com/wp-content/uploads/2021/05/Reported-distance.png)
- Successor = Eigrp Route that has the lowest metric (injected into the routing table)
- Feasible Successor = Back up path (RD < FD of Successor)
EIGRP STUB & Passive Interface
- Improve performance and security of our network
- Stub = Eliminate receiving unnecessary Query Packets
- Passive = Can receive hello messages but sending is disabled in an interface.
VARIANCE COMMAND
- Multiplier to determine the range of acceptable metrics. Anything in this range will be injected into the global routing table.
- EIGRP can load balance between two unequal metric paths, the packet sent to both paths are proportional to the link metric.
MAXIMUM PATH
- The total number of routes to be injected into the global routing table.
EIGRP ROUTE FILTERING
Example: Permit all networks except 10.0.0.0/30 into R7.
![](https://alyxmandario.com/wp-content/uploads/2021/05/Eigrp-Summary.png)
Step 1
Create Prefix-list, ACL, or Route-map.
On R7
Router(config)# ip prefix-list PREFIXNAME seq 10 deny 10.0.0.0/30
Router(config)#ip prefix-list PREFIXNAME seq 20 permit 0.0.0.0/0 le 32
Use Distribution-list
Router(config-router)#distribute-list prefix PREFIXNAME in
- From the R7 perspective, we can’t filter network 10.0.0.0/30 using ACL only. It will drop the Eigrp Neighbor.
- On the R7 routing table, we can have the 50.0.0.0/16 network without dropping the Eigrp neighbor formation, and the 10.0.0.0/30 will not appear in Routing Table.
EIGRP ROUTE-SUMMARY
(Reduce the size of routing table)
Refer to image EIGRP above.
Summary & advertise all the loopback networks of R5
On Router R5 Interface e0/0 type below commands
#ip summary-address Eigrp 100 50.0.0.0/22
Then verify on R6 and R7.
- We can’t advertise network 50.0.0.0/22 under Eigrp, there will be 3 entries in the routing table of R6 and R7.
- But if we summarize and advertise thru “ip summary-address” command there will be only 1 entry in the routing table of R6 and R7.
NAMED EIGRP
- Backward compatible w/ traditional EIGRP.
- Can input multiple address family in a single Named EIGRP. (IPv4, IPv6,)
EIGRP Authentication
- Step 1 Create a Key chain and Key StringsRouter(config)#key chain R1-KEY-CHAINRouter(config-keychain)#key 1Router(config-keychain-key)#key-string PRIMARY-KEYRouter(config-keychain-key)#accept-lifetime 00:00:00 November 1 2020 00:00:00 November 30 2020Router(config-keychain-key)#send-lifetim e 00:00:00 November 1 2020 00:00:00 November 30 2020Router(config-keychain)#key 2Router(config-keychain-key)#key-string SECONDARY-KEYRouter(config-keychain-key)#send-lifetime 00:00:00 November 29 2020 infiniteRouter(config-keychain-key)#accept-lifetime 00:00:00 November 29 2020 infiniteStep 2 Associate Key chain w/ EIGRPRouter(config)#int g0/1Router(config-if)#ip authentication mode eigrp 100 md5Router(config-if)#ip authentication key-chain eigrp 100 R1-KEY-CHAIN##Mirror configuration on the neighbor Router and make sure key-string are the same##
SHOW COMMANDS FOR REFERENCE.
sh ip eigrp neighbour / detail
sh ip eigrp interface
sh ip eigrp topology
sh ip ei topo all-links
sh run int g0/0
sh ip protocol