9.5 Configure BGP to Interact with IGPs
9.5.5 Inject routing information statically into BGP
Listing prefixes with the network command has the same drawbacks as dynamic redistribution. If a route that is listed with the network command goes down, BGP will send an update; if the route comes back, BGP will send another update. If this behavior continues, the IGP instability will translate into BGP instabilities. The only way around this is to use a combination of statically defined prefixes in conjunction with the network command. This will ensure that the prefixes will always remain in the IP routing tables and will always be advertised.

In the previous example, if you wanted to make sure that the fluctuations of route 192.68.10.0/24 do not translate into fluctuations in the BGP, you would include in RTA a static route of the form:

ip route 192.68.10.0 255.255.255.0 Ethernet1

By using the static approach, the prefix entry will always be present in the IP routing table and will always be advertised. The drawback of this approach is that even when a route is down, it will still be advertised by BGP. Considering the gain in network stability compared to the damage an ill-behaved route or multiple ill-behaved routes can cause, administrators may find this approach very efficient.

Note: Click on topology to view command outputs.

The configuration will ensure that 192.68.10.0/24 is always sent. Note that RTA itself is originating the 192.68.10.0/24 prefix and is not relying on the advertisement coming from RTF. If an aggregate is advertised via a static route, it is better to point the static route to null 0 (pit bucket) for loop prevention.