Re: PIM Convergence Problem

John,
you do have pim enabled all way around ? Sparse ? Dense ?
-Carlos

John Neiberger @ 21/04/2013 14:56 -0300 dixit:
> That is what I suspect happened. For some reason, the mroute information
> stayed in place even though unicast routing had changed, which means
> that RPF had changed. A path that was no longer valid or usable was
> still being used to join multicast feeds. Usually, we see the mroutes
> switch immediately to follow the best unicast path, but that didn't
> happen this time and we're stumped as to why. The engineers working when
> it happened didn't clear any routes and didn't get any snapshots, so
> we're stuck with reverse engineering the scenario based on symptoms we
> observed. We can't really recreate it in production without causing
> noticeable problems for people, but we're going to try to recreate it in
> a lab environment. Cisco is going to try to recreate it in the lab, as well.
>
>
> On Sun, Apr 21, 2013 at 11:25 AM, Tony Singh <mothafungla_at_gmail.com
> <mailto:mothafungla_at_gmail.com>> wrote:
>
> makes sense Carlos
>
> John if all else fails clear ip mroute * on the entire path as
> pointed out, what causes this maybe to do with stale mroute
> information not being flushed, check to see if you see this prior to
> doing this
>
> --
> BR
>
> Tony
>
> Sent from my iPad
>
> On 21 Apr 2013, at 12:24, Carlos G Mendioroz <tron_at_huapi.ba.ar
> <mailto:tron_at_huapi.ba.ar>> wrote:
>
> > Hmm,
> > I may be way off, because it is ages since I played with mcast last
> > time, but PIM does not run on top of the IGP/BGP session, it runs
> along
> > and uses the RIB for RPF. If you have pim enabled in the
> interfaces and
> > you tear down the BGP session, PIM does not care. After all, it is
> > independent of the routing protocol, isn't it ?
> >
> > -Carlos
> >
> > John Neiberger @ 20/04/2013 13:49 -0300 dixit:
> >> 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.
> >
> >
> > Rakesh M @ 21/04/2013 08:10 -0300 dixit:
> >> 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 ?
> >>
> >
> > --
> > Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>
> LW7 EQI Argentina
>
>

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
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