Hi Bill, Thanks for your kind explanation.
So far we discussed about having 2 peering links advertising the same prefix, however the routing table would only choose _1_ out of 2 links to send packets. We have a requirement that a client must advertise prefix > /24 only. Does this impose a limitation that if - a /30 is only reachable via the first link only - another /30 is only reachable via second link only (Both /30 are subnets of the advertised /24) Both /30 wouldnt be reachable at the same time, is that right ? (assuming that the 2 routers for both links are not inter-connected, as the latter is used for testing purposes only.) On Fri, Jul 3, 2009 at 10:29 AM, Bill Blackford <[email protected] > wrote: > <snip> > Wouldnt my router be confused with 2 peers advertising the same prefixes ? > How would it decide which peer to send to ? > </snip> > > No. BGP will see both routes in the RIB and select the best path and insert > into the forwarding table. > If all else is equal, chances are the forwarding decision will be based on > the lower IP address, or which peer has the longest uptime. > > You should be fine > > If you issue a 'sh ip bgp' you will see two routes to your clients > destination. One with a ">" indicating the best path which is the one > selected for the forwarding table. My explanation may not be as eloquent as > it should be, but I hope the content of the information is helpful. > > -b > > > -----Original Message----- > From: [email protected] [mailto: > [email protected]] On Behalf Of cc loo > Sent: Thursday, July 02, 2009 6:49 PM > To: cisco-nsp mailing list > Subject: [c-nsp] [BGP] Multiple peering sessions with same ASN/prefixes > possible ? > > Hi all, > > my company's network has a peering connection with a client. > Recently, they requested us to set up another concurrent peering link (for > testing purposes). > > The 2 BGP routers will be advertising the same ASN and prefixes. > As i have limited knowledge in BGP, i wondered if such a set up would screw > up the entire routing for this client ? > > > Wouldnt my router be confused with 2 peers advertising the same prefixes ? > How would it decide which peer to send to ? > > Appreciate your kind advise. Thanks. > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
