Pervasive BGP and routing loops.

Radha Gowda <rxg@proteon.com> Mon, 22 May 1995 22:08 UTC

Message-Id: <199505222101.AA46985@interlock.ans.net>
Sender: ietf-archive-request@IETF.CNRI.Reston.VA.US
From: Radha Gowda <rxg@proteon.com>
Subject: Pervasive BGP and routing loops.
To: bgp@ans.net
Date: Mon, 22 May 1995 16:57:48 -0400 (EDT)
Cc: Radha Gowda <rxg@proteon.com>
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Any comments or suggestions on the following setup (pervasive BGP) would be 
very much appreciated as I consider myself a novice to IP world!


         AS 1            AS 2
	-----            -----
        | 1 | -----/---- | 2 |
        -----            -----
         \                 /
----------\---------------/-----------
	   /             \      AS 3
            \           /
           -----      -----
           | 4 |--/-- | 3 |
           -----      -----
                 IBGP


-  R1 starts advertising route to 128.185.128.0/17 
-  Both R3 and R4 now have two paths to get to 128.185.128.0/17, and the
   best one happens to be via R4.
-  R1 reboots with a changed policy, and starts advertising 128.185.0.0/16
-  During which time (when the connection to R1 is lost) R4 thinks that 
   it can get to 128.185.128.0/17  via R3.
-  R3 thinks it can get to 128.185.128.0/17 via R4.
-  Both R3 and R4 end up pointing to each other as the next hop to get
   to route 128.185.128.0/17.  Neither advertises this new path
   information to the other as the paths learnt from IBGP speakers are 
   not to be advertised back to the sender.  

Is there any good way to resolve this issue than resorting to some sort
of kludge?

Thanks,
Radha

Pervasive BGP and routing loops. Radha Gowda
re: Pervasive BGP and routing loops. toconnor
Re: Pervasive BGP and routing loops. Tony Li
Re: Pervasive BGP and routing loops. Radha Gowda