From: Huan Pham (Huan.Pham@peopletelecom.com.au)
Date: Mon Jul 28 2008 - 20:50:30 ART
Hi Hobbs,
It is required because of the way multicast dense mode works. When a
router receive a mpacket, it floods the multicast packet out to all
other interface, except the interface it is received on.
Let's look at the example provided at the given link, if MA is placed
under a spoke router R2, then RP discovery message sent via 224.0.1.40
can be propogated to R2, then to Hub R1, and further to any router
behind R1, but not to other spoke. This is because, when R1 receives
this "RP discovery message", it floods out all other interface(s), but
not S0.1
If you do sh ip mroute on R1, you will see that the interface S0.1 is
not in the OIL (outgoing interface list) for the group 224.0.1.40.
Similar candidate RP and mapping agent should be communicatable via
224.0.1.39. If they are both spokes, can only be reachable via a hub,
then the MA cannot not event see the RP presence.
Huan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hobbs
Sent: Tuesday, 29 July 2008 8:44 AM
To: Cisco certification
Subject: Re: Why do mapping agents need to be connected to all PIM
routers in NBMA?
btw, I did get it to work with GRE tunnel between the non-hub MA and the
regular PIM spoke. I made these two PIM neighbors over the GRE tunnel.
Just wondering why it is necessary even when you have the scope
argument.
On Mon, Jul 28, 2008 at 4:36 PM, Hobbs <deadheadblues@gmail.com> wrote:
> Hello,
>
> Referring to this doc:
> http://www.cisco.com/en/US/docs/ios/solutions_docs/ip_multicast/White_
> papers/frm_rlay.html
>
> It says that:
>
> "All candidate RPs must be connected to the MA.
> All MAs must be connected to all PIM routers."
>
> Why is the necessary? Isn't this why we have the scope argument on the
> send-rp-announce and send-rp-discovery commands?
>
> Suppose you have a spoke configured as an RP-candidate or MA, are
> there workarounds to make it work?
>
> Thanks,
Blogs and organic groups at http://www.ccie.net
This archive was generated by hypermail 2.1.4 : Mon Aug 04 2008 - 06:11:57 ART