Subject: bgp router id

From: Tulip Rasputin <[email-masked]>
Date: Wed, 26 Nov 2003 20:23:18 -0500 (EST)

Hi,

I noticed a BGP behaviour and just wanted to confirm if it is indeed an anormal thing to happen. I
am not using a loopback IP address nor have I configured a BGP router ID. It thus picks up the
highest IP address available as its Router ID for all the BGP session that it establishes. Now
when this interface goes down it picks up the next highest IP address that is available and uses
it for all subsequent peerings.

Isnt this odd? A single router using 2 different router IDs with two different peers?

I know this is wrong. Either this router should continue with the same old router ID (even though
the interface it not there .. but that hardly matters!) that it had or it should select a new
router ID, break off connections with all the previous peers (very expensive!) and establish new
connections with peers using this new Router ID.

I think it should be the former one. And when it finds that it has no more BGP speakers in FSM
state > OpenConfirm it can update use the new Router ID for all subsequent peerings.

WOuld like to hear your opinion,

Tulip

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From: Mohacsi Janos <[email-masked]>
Date: Thu, 27 Nov 2003 10:41:55 +0100 (CET)

> WOuld like to hear your opinion,

I think, your problem of breaking the connection is implementation
specific. The is rule of thumb configuring router-id if you don't use
loopback address. For example if you use IPv6 only BGP routing (no IPv4
address at all), you have to assign router-id, otherwise BGP does not
start!

Regards,

Janos Mohacsi
Network Engineer, Research Associate
NIIF/HUNGARNET, HUNGARY
Key 00F9AF98: 8645 1312 D249 471B DBAE  21A2 9F52 0D1F 00F9 AF98

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From: Mohacsi Janos <[email-masked]>
Date: Thu, 27 Nov 2003 10:41:55 +0100 (CET)

Regards,

Janos Mohacsi