Re: PIM Convergence Problem

We are not running MSDP and it is all SSM, so there is no RP. It's a fairly
simple setup.

John
On Apr 20, 2013 10:57 AM, "Tony Singh" <mothafungla_at_gmail.com> wrote:

> John
>
> Are we running MSDP here?
>
> I presume RP's are A & D and now B
>
> Is there still reachability between the MSDP peers via BGP somehow
>
> --
> BR
>
> Tony
>
> Sent from my iPad
>
> On 20 Apr 2013, at 17:49, John Neiberger <jneiberger_at_gmail.com> wrote:
>
> > I posted this on cisco-nsp yesterday and didn't get any replies, so I
> > thought I'd run this past the group here.
> >
> > We ran into an interesting problem last night and I'm a little stumped.
> It
> > appears that PIM did not follow a unicast routing change after a BGP peer
> > was shutdown. Imagine this simple topology:
> >
> > [A] ----- [B] ------ [C] ------- [D]
> > |
> > |
> > |
> > [D]
> >
> > Router A is a CRS and is forwarding PIM joins toward Router D, which is
> > directly attached. We are not running an IGP here. There is only an eBGP
> > session between two ASes that we manage. We shutdown the BGP session
> > between A and D, which caused unicast traffic to switch to the path
> toward
> > Router B. However, it looks like Router A did not tear down the PIM joins
> > that are now no longer valid. It seems that it was still joining a lot of
> > traffic that it could no longer do anything with since it would now fail
> > RPF checks.
> >
> > We didn't get snapshots during the event, so I can't prove that is what
> > happened, but it is the only thing we've found that makes any sense.
> We've
> > had quite a few engineers looking at it and we do have TAC on the case,
> but
> > I thought I'd check here, as well.
> >
> > Have any of you seen a situation where PIM joins stay up even when they
> > shouldn't? Is there possibly an issue with an interaction between PIM and
> > BGP? I've never seen this sort of behavior before, so I'm not quite sure
> > what to think.
> >
> > Thanks,
> > John
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Sat Apr 20 2013 - 17:13:03 ART