The Enhanced Interior Gateway Routing Protocol or EIGRP is Cisco proprietary and is a successor and improvement of IGRP. Key points:
1. It is a hybrid distance vector routing protocol.
2. It reacts much faster than RIP to network topology changes.
3. It does not have the hop-count limit of RIP.
4. Sends messages to multicast address 224.0.0.10.
5. It can perform unequal-cost load-balancing.
Configuring EIGRP is almost identical to RIP:
R1(config)# router eigrp 1
R1(config-router)# no auto-summary
R1(config-router)# network 10.5.3.0
R1(config-router)# network 192.168.2.0 0.0.0.255
R1(config-router)# passive-interface gi 2/0
The “1” in the first command states the Autonomous System number of our networks. It can be any number but it has to be the same across our routers or no adjacency and route sharing will occur.
As with RIP the “network command” is by default classful. So the “network 10.5.3.0” will include all interfaces in the range 10.0.0.0/8. As can be seen in the second network command though, we can specify a wildcard so that only those interfaces in the given netmask are included. The wildcard is the bit reverse of the netmask so the “0.0.0.255” equates to the netmask “255.255.255.0”. If we have a router and we only want to include a few interfaces, we can just specify their IPs in separate network commands with the “0.0.0.0” wildcard -> 255.255.255.255 -> /32.
To get the info we need on the routing protocol we use:
R1# show ip protocols
*** IP Routing is NSF aware ***
Routing Protocol is “eigrp 1”
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks flagged in incoming updates
EIGRP-IPv4 Protocol for AS(1)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID: 1.1.1.1
Topology: 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
Automatic Summarization: disabled
Maximum path: 4
Routing for Networks:
10.0.0.0
192.168.2.0/24
Passive Interface(s):
GigabitEthernet2/0
Routing Information Sources:
Gateway Distance Last Update
2.2.2.2 90 00:00:22
3.3.3.3 90 00:00:21
Distance: internal 90 external 170
The information shown is very similar to that for RIP in the previous page but with some additions: Autonomous System, Router-ID, Administrative Distance (90 & 170), max hops and the metrics EIGRP uses to calculate the route costs.
As with RIP, the maximum number of paths EIGRP will use for any given route is 4 by default but we can change it:
R1(config-router)# maximum-paths 6
The Router-ID can be set manually:
R1(config-router)# eigrp router-id 1.1.1.1
If we do not do that, it is set to:
• the highest IP address of any local loopback interface
• the highest IP address of any local physical interface
It is best practice to create at least one loopback interface on the router