Re: Please don't use 11.1-MFIB with DVMRP-mode tunnels

[Göran Bengtson <]

On Mon, 6 Apr 1998, Bill Fenner wrote:

> From: Bill Fenner fenner@localhost
> To: Göran Bengtson goeran@localhost
> Cc: "John M. Zwiebel" jzwiebel@localhost, David Meyer dmm@localhost,
>     fenner@localhost, mbone-eu-op@localhost, mbone@localhost
> Message-ID: <98Apr6.153342pdt.177482@localhost>
> Date: Mon, 6 Apr 1998 15:33:29 PDT
> Subject: Re: Please don't use 11.1-MFIB with DVMRP-mode tunnels 
> 
> Since IOS doesn't accept prunes from DVMRP neighbors on a LAN, you should
> never have DVMRP neighbors on a LAN anyway, so the fact that it doesn't
> work shouldn't be an issue.

I pointed at the fact that when conditional flooding was implemeted, DVMRP-
interaction with a DVMRP-neighbors on LAN (10Mbps Ethernet in our case) ceased
to work, or to be more specific - the INTERACTION works but the output
interface to the downstream DVMRP-neighbor is never put in the O-list of a
(S,G) entry (S is upstreams from the DVMRP-router). From the description of
how and why the "conditional flooding" was implemented, I can understand that
a bug could be introduced.

DVMRP-interaction does otherwise work (and has done so for a long time) for
LAN DVMRP-neighbors when using "ip dvmrp unicast-routing" on the interface. I
don't believe that is a coincidence. Furthermore, unless that documentation is
totaly wrong, it states that it should work - se below for some excerpts. 

"PIM routers dynamically discover DVMRP multicast routers on attached networks."

"When Cisco routers are directly connected to DVMRP routers OR interoperate
with DVMRP routers over an MBONE tunnel."

"When a Cisco router runs DVMRP over a tunnel, it advertises sources in DVMRP
Report messages much as it does on real networks."

"By default, only 7000 DVMRP routes will be advertised over an interface
enabled to run DVMRP (that is, a DVMRP tunnel, an interface where a DVMRP
neighbor has been discovered, or an interface configured to run ip dvmrp
uncast-routing)."

> 
>   Bill

			/ Göran Bengtson