Lab 54 - EIGRP Default Route Advertisement

Prerequisites: CCNP level skills.

Topology

Pic. 1 - Topology Diagram.

Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task1
Make R4 the gateway of the last resort for all routers. Use the following methods (always remove the previous one before proceeding to the new one):

1. Using summary route.
2. Using 'network 0.0.0.0'.
3. Using the default route redistribution.
4. Using 'ip default-network' statement.

Lab Solution

Task 1

Make R4 the gateway of the last resort for all routers. Use the following methods (always remove the previous one before proceeding to the new one):

Method 1 - Summary Route

R4 Configuration:

!

interface FastEthernet1/0
 ip address 10.1.124.4 255.255.255.0
 ip summary-address eigrp 1 0.0.0.0 0.0.0.0 5

!

Method 2 - Network 0.0.0.0

R4 Configuration:

!

ip route 0.0.0.0 0.0.0.0 null0

!

router eigrp 1
 network 10.1.124.4 0.0.0.0
 network 172.16.104.4 0.0.0.0
 network 172.16.144.4 0.0.0.0
 network 0.0.0.0
 no auto-summary

!

Method 3 - Default Route Redistribution

R4 Configuration:

!

ip route 0.0.0.0 0.0.0.0 Null0

!

router eigrp 1
 redistribute static
 network 10.1.124.4 0.0.0.0
 network 172.16.104.4 0.0.0.0
 network 172.16.144.4 0.0.0.0
 no auto-summary

!

Method 4 - IP Default-Network

Note!

This method comes from IGRP. It assumes that the router will use the default network rather than default route (0.0.0.0). The method has two stipulations:

• the network advertised as the gateway of last resort must belong to a class A, B, or C network
• the network advertised as the gateway of last resort must not be directly connected to the advertising router (must be learned)

In order to overcome these stipulations the following will work:

R4 Configuration:

!

ip default-network 172.16.104.0

!

Verification:

This step results in creating the following entry:

Pic. 2 - R4's Routing Table.

Since the classful entry now appears in the routing table, the following configuration will create default network on R4. (the network of the last resort).

R4 Configuration:

!

ip default-network 172.16.0.0

!

The above command replaces the previous one and results with:

Pic. 3 -  R4's Routing Table.

The last step is to redistribute this static entry into EIGRP in order to advertise the gateway of the last resort to R4's EIGRP neighbors.

R4 Configuration:

!

router eigrp 1
 redistribute static
 network 10.1.124.4 0.0.0.0
 network 172.16.104.4 0.0.0.0
 network 172.16.144.4 0.0.0.0
 no auto-summary

!

This results in advertising default network (*)

Pic. 4 - R1's Routing Table.