Re: PIM Convergence Problem

Hi,

We had a similar issue with Juniper if my memory goes right. It wont
refresh until we manually give a clear command. Did you try clearing Pim ?
Would everything get restored if you bring back the link between A and D ?

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On Sun, Apr 21, 2013 at 4:43 AM, John Neiberger <jneiberger_at_gmail.com>wrote:
> 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 that are now no longer valid.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
> > >
> > >
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