From: ccie2be (ccie2be@nyc.rr.com)
Date: Sat Oct 23 2004 - 18:12:54 GMT-3
Hi Bob,
AFAIK, ip pim nbma isn't supported for dense mode - it only works for sparse
or sparse-dense-mode.
But, I'm not sure I understand what you mean when you say, "the multipoint
interface must be on the path to the RP if nbma-mode is going work to allow
sparse-mode flows into and back out of the hub on the same multipoint
interface."
Do you mean that the RP can't be configured on or behind a spoke router in a
hub and spoke partial mesh even if the MA is configured on or behind the hub
router? If so, why not?
Tim
----- Original Message -----
From: "Bob Sinclair" <bsin@cox.net>
To: "Cisco certification" <ccielab@groupstudy.com>
Sent: Saturday, October 23, 2004 4:06 PM
Subject: Re: Multicast over NBMA
> Tim,
>
> It is important to have the MA at the hub if you are distributing the
> 224.0.1.40 group in dense mode. NBMA-mode is not effective for dense mode
> flows, since dense mode does not send the *,G entries that NBMA-mode
relies
> upon to populate the OIL.
>
> The prune-override function of nbma-mode is well-documented, but its
ability
> to overcome the hub-and-spoke-OIL problem is not, IMHO.
>
> We lab this up in NMC-1 class, and it is our experience that the
multipoint
> interface must be on the path to the RP if nbma-mode is going work to
allow
> sparse-mode flows into and back out of the hub on the same multipoint
> interface.
>
> Bob Sinclair
> CCIE #10427, CISSP, MCSE
> www.netmasterclass.net
>
> ----- Original Message -----
> From: "ccie2be" <ccie2be@nyc.rr.com>
> To: "Bob Sinclair" <bsin@cox.net>; "AK Singh" <singh.anand@gmail.com>;
> "Cisco certification" <ccielab@groupstudy.com>
> Sent: Saturday, October 23, 2004 2:34 PM
> Subject: Re: Multicast over NBMA
>
>
> > 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
> >> >>
> >> >>
This archive was generated by hypermail 2.1.4 : Sat Nov 06 2004 - 17:11:52 GMT-3