BGP filters...

jason_lunde

So just a quick question...these two commands did not do the same thing in my lab, but I had expected them to. What I thought was that either way they would block the same network from being advertised to a router (neighbor 192.168.1.5, out of serial 0)

I set up a prefix list (superonly) allowing the networks I wanted through, and then issued this command:

SanJose2(config-router)neighbor 192.168.1.5 prefix-list superonly out
(RESULT-The proper network was blocked)

I thought that I could give this command and get the same results:

SanJose2(config-router)#distribute-list prefix superonly out serial 0
(RESULT- The network that I wanted blocked was allowed through)

So can anyone clear my confusion on these two commands. I merely thought that the first one, defining the neighbor was more specific. The second I thought would block the network from any downstream routers out of s0.

thanks in advance guys.

networker050184

That is one of those commands that is there even though it doesn't work. The distribute-list command does work when redistributing though.

kryolla

it works you just have to play with it or it might be just for neighbors. Did you reset the neighbor

After playing with this you can't filter routes out an interface but per neighbor with the nieghbor command or all neighbors with distribute-list.

BGP prefixes or NLRI are advertised per neighbor and not per interface as in IGP

networker050184

kryolla wrote: »

it works you just have to play with it or it might be just for neighbors. Did you reset the neighbor

After playing with this you can't filter routes out an interface but per neighbor with the nieghbor command or all neighbors with distribute-list.

BGP prefixes or NLRI are advertised per neighbor and not per interface as in IGP

Yes it works great for neighbors, but even though the interface key word is there it doesn't do anything.