From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Fri May 14 2004 - 16:58:54 GMT-3
At 3:18 PM -0400 5/14/04, gladston@br.ibm.com wrote:
>Hi,
>
>I think it is a basic question, but could not find it on the Archive.
>
>Router 1 is on AS 124, as router 2 and router 3. R1 peers with R2
>and R3. Router R1 is RR. Router 3 peer with router 4 on AS 34.
>Router 1, 2, 3, and 4 are also on AS 1234. Router 4 peer with
>external neighbor 7, on AS 777.
>
>Router 777 is advertising net 7.7.7.7. If I configure dampening on
>R4 for net 7.7.7.7, when the route flaps it is dampened. If I
>configure dampening on R3 for net 7.7.7.7, when the route flaps it
>is not dampened and it is ok because Cisco says external routes are
>not dampened if received from iBGP.
>
>Now, I am not sure about this:
>Router 1 is advertising 1.1.1.1. If I configure dampening on R2 for
>net 1.1.1.1, when the route flaps it is not dampened. I did not find
>a statement saying that internal networks from iBGP peers should be
>dampened, but I concluded it based on the statement "external routes
>are not dampened if received from iBGP". (I concluded that if
>external routes are not dampened, internal routes are dampened, but
>would like to check it).
>
>Based on the result of the lab I would say that internal networks
>from iBGP peers are not dampened. Is it corrected or should I tried
>on more time?
Well, I find it very hard to think of why anyone would dampen
internal routes in an ISP network. Of course, ISPs don't to stupid
lab-like things such as redistributing large numbers of IGP routes
into BGP.
It would be consistent with everything I know of BGP protocol
implementation that you wouldn't damp internal routes. If an internal
route is flapping, it's either bad network design or some software
gone totally crazy. I don't think Cisco will implement strange
behavior just to have it in the lab...I think.
This archive was generated by hypermail 2.1.4 : Wed Jun 02 2004 - 11:12:12 GMT-3