[c-nsp] Source address on BGP peering set up

[Erdem Sener]

Hi, 

 You could also specify 'bgp router-id' under 'router bgp xxx' section.

 Cheers,
 Erdem 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Mark Tinka
Sent: Friday, January 14, 2005 3:46 PM
To: cisco-nsp at puck.nether.net; Piltrafilla
Subject: Re: [c-nsp] Source address on BGP peering set up

On Friday 14 January 2005 15:14, Piltrafilla wrote:
> Hi people,

Hello.

>
> Anyone knows how BGP on a Cisco router choose source IP address for 
> peering establishment if no "update-source" command is applied to 
> neighbor? Is it only the primary IP address on the closest interface 
> to neighbor?

Without manually specifying your source interface, BGP will find and use
the Loopback interface with the highest IP address. Failing that, it
will take the next highest IP address configured on the router
(regardless of interface).

This can become a problem, especially if you keep adding/removing IP
addresses on your router (customers, new routers, new segments, e.t.c.),
hence the elegance of 'update-source'.

Mark.

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