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Setting a Static Default Route

You might not want your routers to rely on dynamically learned default routes. Instead, you might prefer to specify a static default route that your routers use to forward traffic when they do not have a routing entry for a destination. Use the ip route command to configure a default route on a router. The static route can point to a network number, an IP address, or a physical interface. You can add a distance value to give preference to a specific static route when multiple entries exist for the same route.

Suppose that in Figure 16, router KC has been configured to advertise a default route to router Chicago:



host1(config)#router bgp 62 

host1(config-router)#network 172.17.24.0 mask
255.255.248.0 

host1(config-router)#neighbor 10.8.3.1 remote-as
21 

host1(config-router)#neighbor 10.8.3.1 default-originate

You prefer that router Chicago send traffic with unknown destinations to router StLouis, so you configure a static default route on router Chicago:



host2(config)#router bgp 21 

host2(config-router)#network 192.168.48.0
mask 255.255.240.0 

host2(config-router)#neighbor 10.8.3.4 remote-as
62 

host2(config-router)#neighbor 10.24.5.1 remote-as
37 

host2(config-router)#exit 

host2(config)#ip route 0.0.0.0 0.0.0.0 172.25.122.0

Router StLouis is configured to advertise network 172.25.122.0/23 to router Chicago:



host3(config)#router bgp 37 

host3(config-router)#network 172.25.122.0
mask 255.255.254.0 

host3(config-router)#neighbor 10.24.5.3 remote-as
21

Figure 16: Setting a Static Default Route

Image g013174.gif

ip route

Use to establish static routes.
Use the no version to remove static routes.
See ip route.

neighbor default-originate

Use to cause a BGP speaker (the local router) to send the default route 0.0.0.0/0 to a neighbor for use as a default route.
Use the route-map keyword to specify outbound route maps to apply to the default route. The route map can modify the attributes of the default route.
If you specify a BGP peer group by using the peerGroupName argument, all the members of the peer group inherit the characteristic configured with this command. You cannot override the characteristic for a specific member of the peer group.
Outbound policy configured for the neighbor (using the neighbor route-map out command) is not applied to default routes that are advertised because of the neighbor default-originate command.
This command takes effect immediately.
Use the no version to prevent the default route from being advertised by BGP. Use the default version to remove the explicit configuration from the peer or peer group and reestablish inheritance of the feature configuration.
See neighbor default-originate.

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