[c-nsp] [BGP] Multiple peering sessions with same ASN/prefixes possible ?

[Bill Blackford]

<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: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] 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.
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