From: ccie2be (ccie2be@nyc.rr.com)
Date: Sun Oct 24 2004 - 10:54:11 GMT-3
Hey Bob,
Thanks, that's a great example.
But, what happens when R2, the RP, receives a join from a directly connected
or downstream client? Wouldn't
R2 try to create a SPT to the source by sending a (S, G) Join rather than a
(*,G) join to R1 which R1
would then forward to R3?
I'm a little fuzzy on this because I don't know how R2 would know where the
source is unless the source were already sending traffic.
Tim
----- Original Message -----
From: "Bob Sinclair" <bsin@cox.net>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Cisco certification"
<ccielab@groupstudy.com>
Sent: Saturday, October 23, 2004 5:28 PM
Subject: Re: Multicast over NBMA
> Tim,
>
> Suppose R1 is the hub and R2 and R3 are the spokes. You want to send
> multicast from R3 to R2, or a client behind R2. Given this frame-relay
> hub-and-spoke topology, that stream will have to go into and back out of
the
> R1 frame-relay multipoint interface. If you put the RP on R2, then R1
will
> never receive a *,G from R2 for the multicast group, and R1 will not put
R2
> on the outgoing interface. If you place the RP on R1 or R3 (so that R1
sees
> the *,G), then R2 will go on the OIL and the sparse-mode flow will work
from
> spoke to spoke. This is our experience. But again, I have not seen the
> ability of nbma-mode to permit sparse-mode traffic from spoke to spoke
> documented.
>
> HTH,
>
> Bob Sinclair
> CCIE #10427, CISSP, MCSE
> www.netmasterclass.net
>
> ----- Original Message -----
> From: "ccie2be" <ccie2be@nyc.rr.com>
> To: "Bob Sinclair" <bsin@cox.net>; "Cisco certification"
> <ccielab@groupstudy.com>
> Sent: Saturday, October 23, 2004 5:12 PM
> Subject: Re: Multicast over NBMA
>
>
> > 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
> >> >> >>
> >> >> >>
> > _______________________________________________________________________
> >> >> >> Subscription information may be found at:
> >> >> >> http://www.groupstudy.com/list/CCIELab.html
> >> >> >
> >> >> >
> > _______________________________________________________________________
> >> >> > Subscription information may be found at:
> >> >> > http://www.groupstudy.com/list/CCIELab.html
> >> >
> >> >
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