Subject: PIM dense mode and CGMP

From: Andy McConnell <[email-masked]>
Date: Mon, 22 Jun 1998 14:49:08 -0700 (PDT)

Here is an interesting problem:

                (VLANS on two Catalyst 5000
		 switches with CGMP enabled )

                 Multicasters VLAN 3______
                                          \
Cisco 7206-------Multicasters VLAN 2       \Cisco 7206-<pim>-7206--(to 
   (GW1)  \                                /   (GW2)                MBONE)
	   X_____Multicasters VLAN 1______/

On the 4 router interfaces to the VLANs shown:

	ip pim dense-mode
	ip cgmp

Problem:  When GW1's interface to VLAN1 ("X") is pim enabled, no prune
messages are sent to GW2... causing the MBONE to flood in over the link
labeled <pim> above, which is a T1. 

All routers are running 11.2-10aP.  Both switches are running 2.4.4.  

I've been able to eliminate the possibility of a stray mrouter on all of
the other multicasters VLANs, so I don't think that's wrong.  Likewise,
there are no DVMRP speakers on these VLANs.

I can only imagine that there's something wrong with the interaction
between CGMP and PIM that's causing this to happen.  

Can anyone recommend the right settings to use? i.e., turn off cgmp in key
places where it may not be necessary?  Or, not use cgmp at all? 

-Andy

--
Andy McConnell       アンディ マッコネル
Network Architect, NTT Multimedia Communications Laboratories

Chaos reigns within.
Reflect, repent, and reboot.
Order shall return.

	-- Haiku by Suzie Wagner

---

From: Dino Farinacci <[email-masked]>
Date: Tue, 23 Jun 1998 00:11:29 -0700 (PDT)

>> between CGMP and PIM that's causing this to happen.  

    Your probably RPF failing on VLAN 1 so the packets are silently discarded
    if there are no routes cached for the MBONE sources. Do a "show ip rpf
    <mbone-source>" so see which interface or VLAN your RPFing to, if any.

Dino

---

From: Andy McConnell <[email-masked]>
Date: Tue, 23 Jun 1998 10:37:57 -0700 (PDT)

Thanks!  I think that was the problem.

BTW - moved to sparse mode instead... much nicer. :-)

-Andy

With every passing hour our solar system comes forty-three
thousand miles closer to globular cluster 13 in the
constellation Hercules, and still there are some misfits who
continue to insist that there is no such thing as progress.
                               -- Ransom K. Ferm