From: ccie2be (ccie2be@nyc.rr.com)
Date: Sat Oct 23 2004 - 15:34:56 GMT-3
Hi Bob,
I'm not sure we're saying different things. I was going by what Beau
Willianson wrote in his book Developing IP Multicast networks on page 458 -
460.
In his example, the RP is behind a spoke router, but the MA is behind the
hub router. The network is, of course, running Auto-RP.
With the RP behind one of the spoke routers, the other spoke routers don't
hear the rp annouce messages from the rp, but the MA behind the hub does.
And, since the MA then sends out the rp to group mappings, all the spoke
routers hear them. Is this not correct?
And, when the hub is configured with ip pim nbma mode, joins and prunes from
the spoke routers don't affect joins and prunes from other spoke routers.
Have anything changed since this was written or am I mis-understanding
something critical?
Tim
----- Original Message -----
From: "Bob Sinclair" <bsin@cox.net>
To: "ccie2be" <ccie2be@nyc.rr.com>; "AK Singh" <singh.anand@gmail.com>;
"Cisco certification" <ccielab@groupstudy.com>
Sent: Saturday, October 23, 2004 12:07 PM
Subject: Re: Multicast over NBMA
> Tim,
>
> If you are saying that the placement of the RP is irrelevant to the
> operation of PIM NBMA-mode in AK's scenario, then I beg to differ. If the
> hub interface is not on the path between the spoke and the RP, then the
hub
> will not receive a *,G from that spoke, that spoke will not show up on the
> hub's OIL, and it will not receive multicast traffic from another spoke.
> Lab it up.
>
>
> Bob Sinclair
> CCIE #10427, CISSP, MCSE
> www.netmasterclass.net
>
> ----- Original Message -----
> From: "ccie2be" <ccie2be@nyc.rr.com>
> To: "AK Singh" <singh.anand@gmail.com>; "Cisco certification"
> <ccielab@groupstudy.com>
> Sent: Saturday, October 23, 2004 11:24 AM
> Subject: Re: Multicast over NBMA
>
>
> > The way I understand it, it's not the placement of the rp that matters
as
> > far as reachability is concerned. It's the placement of the Mapping
> > Agent.
> > Also, this issue is only relevant when running Auto-rp. It's not an
issue
> > if using static rp or BSR.
> >
> > You are correct about not needing a tunnel between the spokes when ip
pim
> > nbma is running on the hub, but do you understand why that is?
> >
> > In case you don't, here's the reason. Without ip pim nbma on the hub,
> > when
> > a mcast stream starts flowing from the hub to the spokes assuming one
> > spoke
> > wants the stream but the other spoke doesn't, the spoke that doesn't
want
> > the stream sends a prune up to the hub.
> >
> > Without nbma mode on the hub, the hub doesn't realize that one of the
> > spokes
> > still wants the mcast stream. So, since the hub has only one interface
to
> > reach both spokes and it now gets a prune message, it removes that
> > interface
> > from the outgoing interface list (OIL) and stops the mcast stream from
> > reaching either spoke.
> >
> > With nbma mode, the OIL contains both spokes. So, when the hub gets a
> > prune
> > from just one of the spokes, it only removes that one spoke from it's
OIL.
> > The other spoke continues to receive the mcast stream.
> >
> > For more details on this, look for the mcast training presentations
slides
> > on cisco.com
> >
> > HTH, Tim
> >
> >
> > ----- Original Message -----
> > From: "AK Singh" <singh.anand@gmail.com>
> > To: "Cisco certification" <ccielab@groupstudy.com>
> > Sent: Saturday, October 23, 2004 10:14 AM
> > Subject: Multicast over NBMA
> >
> >
> >> Hello folks,
> >>
> >> I know thie topic has been discussed in several ways on this alias. I
> >> searched but couldn't get a direct answer hence posting on this alias.
> >> Appreciate any response.
> >>
> >> Let us say we are running pim in sparse mode and we have take RP
> >> issues (i .e spokes are learning correct RPs, the RP is places a
> >> router which is on top of hub and we are using autorp listener).
> >>
> >> Now when to send a feed (ping to the group) from one of the spoke to a
> >> group on other spoke, do we always need a tunnel to be created between
> >> spokes for this?
> >>
> >> Here is my undestanding (please correct me), we don't need tunnel
> >> between spokes when we are using either:
> >>
> >> 1) pim nbma mode
> >> 2) spokes have brodcast capability between them.
> >>
> >> When else do we need? Any more lights on this topic.
> >>
> >> Thanks
> >> -Anand
> >>
> >> _______________________________________________________________________
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> >
> > _______________________________________________________________________
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