Subject: RE: Cisco's DVMRP Discovery ?

From: "Jesus Maria Arango - Ing. Comunicaciones FSM LTDA." <[email-masked]>
Date: Wed, 5 Mar 1997 12:06:40 +0500 (GMT)

On Wed, 5 Mar 1997, Dave Rubin wrote:

> I don't think it works quite that way.
> 
> Ciscos do not actually implement DVMRP. They can, however, maintain a 
> DVMRP routing table. When this is the case, PIM uses DVMRP routes when
> they exist, instead of using the unicast routing protocol.   The forwarding
> of multicast packets is actually handled by PIM, but it could utilize the 
> DVMRP routing table for RPF.

It's really a matter of names I guess. It doesn't matter how you call the
process. What matters is the algorithm and the types of packets that are
being exchanged. What I meant to say is that the router is using DVMRP
algorithm when forwarding packets comming from the tunnel, they are also
exchanging DVMRP routes and I would think that  prunes and grafts are also
in DVMRP encapsulation. This is where I want to know if I am right, but
you can call the process PIM if you want.

> I'm not 100% clear on exactly how it works ... you might want to contact 
> [email-masked] for more info. I use DVMRP routing over GRE 
> tunnels running PIM, and it works fine ... as long as you are very
> careful with the "ip dvmrp unicast-routing" command (which when improperly
> configured can inject your entire unicast routing table into DVMRP).

Would you explain this routing injection problem to me ?

- Jesus

---

From: "Daniel A. Alvarez" <[email-masked]>
Date: Wed, 05 Mar 1997 10:07:56 -0800

> you can call the process PIM if you want.

	NO, on the GRE tunnel all the messages are PIM messages,
	no DVMRP messages are sent.

	The forwarding is also done by the PIM algorithm and not
	DVMRP.

dan