Routing

hello

dear juniper

if there are 2 router  r1 and r2 are set as RR which has different cluster id

r3 peer with r1 as RR client ,r4 connect to r2 as RR client

 I 'd like to know how junos handle RR with different cluster id

whether r1 will send route of r3 to r2?

pls

Yes , in this case r1 will send route of r3 to r2 , Provided r1 and r2 has ibgp session..

http://www.juniper.net/techpubs/software/junos-security/junos-security10.2/junos-security-swconfig-interfaces-and-routing/topic-47193.html

  If you configure a peer as RR Client, then will override the rule "dont propagete ibgp prefix to ibgp peers". The cluster id is used to avoid routing loops. This way each RR knows that a prefix comes from a RR in the same cluster. If the RR receive its own cluster id in a prefix will discard that prefix because this is a potential route loop. If the cluster id are not the same, will accept the route, but cluster id are used when you have more tan 1 RR in the same cluster, if you dont configure this will use the router id.

  This is not usual to peer RR, these should peer with the edge ebgp peers, and internal ibgp peers. Usually, each internal ibgp peers with each RR, so there is no need to peer both RR.

  If your topology need to propagate ibgp learned prefix to other ibgp peers, and you have to peer the RR to get this, then maybe you may take other solution, like Confederations.

  Confederations is the right way to propagate ibgp learned prefix to other ibgp internal peers, if you cant have a full mesh ibgp topology. Route reflectors are useless if each ibgp peer have only a peering with one RR. I you lost that RR will lost all ibgp peers.

thanks,Alex and jstar

     | INTERNET    |        
        |                         |        
        |                         |        
        |                         |        
      router1-----router2      
       |     |             |        |     
      |           |   |            |      
     |          |        |            |       
    |       |                 |       |        
  router3              router4

1:here is my topo

ospf is running for ibgp neigbor connection

r1 r2 r3 r4 are ibgp

r3 peer with r1/r2 as normal ibgp session

r4 peer with r1/r2 as normal ibgp session

r1 peer with r2 as normal ibgp session

because r3 can't talk to r4

now I am planning to

set r1 and r2 as RR with same cluster id

r1 peer r3 r4 as  RR server

r2 peer r3 r4 as RR server

normal ibgp session between r1 and r2

is it fine?

 2:btw:if r1 r2 have different clustid ,they will treat other as non-client,right?

Hi.

Your configuration is right, but R1 and R2 should have the same cluster-id and should be RR clients each other.

But the cluster-id is not used to establish the client or not client relation. You configure this in the server, to send ibgp learned prefix to an ibgp peer. Each RR server dont know if the other is a RR server, but if receive prefixwith its own cluster-id, will delete this.

what will happen if r1 r2 don't peer each other as RR client?

would u like to how me a example

I am interested in this

thanks in advance

 There will happen nothing, because cliens have a redundant connection to each RR, this way, if a internet connection fails, or a RR fails, or the client to a RR path fail, there will be a exit/incoming path through the other RR.

  Think that if you peer your RR, there is only one peer more to get a full mesh ibgp, from both clients. Of course if you have 10 ibgp clients this is not the case.

 If clients cant have a ibgp connection with each RR, a redundant connection, or you need the incoming traffic to get into your AS through a specific internet connection for some prefix, and others prefix through the other connection, you will need to peer both RR. This way a client will have always a incoming path from both internet connections.

  You have to be carefull with which routers propagate the prefixes. if you learn and propagate from your ibgp, will need redundant ibgp connections, both client to RR, or RR to RR. This way will assure prefix are propagated outside.

  If you use your ebgp routers to propagate internal prefixes, have to be carefull to dont lost connection with its internal routers. Because you will propagate something you cant reach. In this case, if you lost your RR connection and each client dont peer with each RR, then will lost the path to internal peers from the ebgp router. In this case you will need to peer RR and each client with both RR.

  Or use a conditional route advertisement, to avoid propagate prefix you cant reach from that router.

  There is many cases, depends on how you use your internet connections, and from where you propagate the prefix. There should be always a redundant path, and have to be sure to dont propagate unreachable paths.

hello,Alex

in my opinion,I 'd like to peer r1 r2(both of them are RR) as normal ibgp connection instead of RR client

is it fine?

r1 and r2 are 2 routers which face Internet

r3 and r4 connect to r1 and r2 via loopback int as ibgp neigbhor

Of course you could. But will not be used by r3 and r4, since prefix will have higher metric than direct ibgp to r2 or to r1. This will be a backup for everything connected directly to r1 or r2, if that router lost its ebgp peer.