Subject: Cisco to Sun mrouted problem

From: Matthew Idema <[email-masked]>
Date: Mon, 15 Dec 1997 18:40:44 -0600

I'm trying to get multicast going on a network that contains three Cisco
routers and a Sun Ultra1 (running mrouted 3.8).  The router immediately
upstream of the Ultra1 doesn't seem to be sending a membership report to
mrouted.

I can get the entire network to route packets if machines on the Sun's
two interfaces are active in the group (mrouted logs a "membership
report"), but if I try it with no participants on the interface the Sun
shares with the Cisco, it doesn't work and I don't see any "membership
reports" in the mrouted debug statements.

The Cisco's configs include "multicast enable" and "pim-dense-mode."
Any suggestions would be very helpful, I've been working on this for
weeks and can't get it right.

Matt I.
[email-masked]

---

From: Matthew Idema <[email-masked]>
Date: Tue, 16 Dec 1997 08:34:01 -0600

An addendum:

There are no active hosts (shown as H) on any of the network segments
between the Sun and the three Ciscos (shown as R):

H -- R -- R -- R -- Sun -- H

Could this be part of the problem?  Do I need a tunnel?

---

From: "John M. Zwiebel" <[email-masked]>
Date: Tue, 16 Dec 1997 09:54:26 -0800

An addendum:

    1    1    2    3           2

You do not need a tunnel.

I have to make some assumptions about what it is you are trying to do. 
The first being that your two hosts are both members of the same group and
both are sending packets to the group.  If this is the case, mpackets from
H1 are forwarded via pim dense mode to R3.  R3 notes that it has a
dvmrp router (the Sun) on an outgoing interface so it does not Prune that
interface but forwards the mpackets.  R3 also should be sending IGMP host
reports to the Sun.  Depending on the version of IOS you are running,
these may be version 1 or version 2 reports.  At one time, the routers all
listened for the reports that were being sent across the network and if a
version 1 report was discovered, all the cisco's would default to version 1.
Since there wasn't any way of moving back to IGMP version 2, it is now
required that you choose which IGMP version you want to use. 

Part of the output from "sh ip igmp int" is:

     IGMP querying router is 171.69.214.9  
     DVMRP/mrouted neighbors present for 00:00:15
	[version  0.0] [flags: ]
     1 DVMRP neighbor up transitions since system restart
     0 DVMRP routes + 0 poison-reverse routes received in last 00:00:15
     2/0 Unicast/DVMRP routes last advertised by DVMRP

Which tells you that the cisco router does see the mrouted system.     
You can also discover which system is the IGMP querier and the version the
router is running.

Now that R3 has a (*,G) (because it has an (s,g)), it sends IGMP host
reports to the sun when it receives an IGMP query.

"deb ip igmp" will show you this.

   Dec 16 09:11:16.522: IGMP: Send v2 Report for 224.0.1.39 on Ethernet0/0

When the sun receives this membership report it will forward mpackets for
h2.  

An alternative would be to configure "ip dvmrp unicast-routing" on R3.  This
will propogate DVMRP routes to all your cisco's so RPF lookups can be made
on those routes rather than the unicast routes.  This is important to do
on networks where the unicast and multicast topologies are not congruent,
which may be your case.
    
    > weeks and can't get it right.

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	John Zwiebel                       Phone: 408-526-5303
	Cisco Systems Inc.                 
	Multimedia Group