Cisco Systems 78-11741-02 manual Overriding Static Routes with Dynamic Protocols Example, IPC-380

Configuring IP Routing Protocol-Independent Features

IP Routing Protocol-Independent Configuration Examples

Overriding Static Routes with Dynamic Protocols Example

In the following example, packets for network 10.0.0.0 from Router B (where the static route is installed) will be routed through 172.18.3.4 if a route with an administrative distance less than 110 is not available. Figure 62 illustrates this example. The route learned by a protocol with an administrative distance of less than 110 might cause Router B to send traffic destined for network 10.0.0.0 via the alternate path—through Router D.

ip route 10.0.0.0 255.0.0.0 172.18.3.4 110

Figure 62 Overriding Static Routes

Router A

Router B

172.18.3.4

Router C

Router D

10.0.0.0

1269a

Administrative Distance Examples

In the following example, the router igrp global configuration command sets up IGRP routing in autonomous system 1. The network router configuration commands specify IGRP routing on networks 192.168.7.0 and 172.16.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance command sets the administrative distance to 90 for all routers on the Class C network 192.168.7.0. The third distance command sets the administrative distance to 120 for the router with the address 172.16.1.3.

router igrp 1 network 192.168.7.0 network 172.16.0.0 distance 255

distance 90 192.168.7.0 0.0.0.255 distance 120 172.16.1.3 0.0.0.0

The following example assigns the router with the address 192.168.7.18 an administrative distance of

100 and all other routers on subnet 192.168.7.0 an administrative distance of 200:

distance 100 192.168.7.18 0.0.0.0 distance 200 192.168.7.0 0.0.0.255

However, if you reverse the order of these two commands, all routers on subnet 192.168.7.0 are assigned an administrative distance of 200, including the router at address 192.168.7.18:

distance 200 192.168.7.0 0.0.0.255 distance 100 192.168.7.18 0.0.0.0

Cisco IOS IP Configuration Guide

IPC-380