Subject: "Multihome" multicast routing

From: "Forrest W. Christian" <[email-masked]>
Date: Fri, 7 Nov 1997 00:30:04 -0700 (MST)

We're about 60 days out from getting our second line to the net, so I'm
starting to look at various services and trying to prepare them for the
transition.  

One of them that I'm currently looking at is our mbone feed.  Right now,
mbone tends to be a fairly light load on our system, with our tunnel to
Sprint being idle most of the time.  However, when there has been an event
that I've wanted to "attend", about 50% of the time I've been less than
happy with the quality of the feed.  As far as I can tell, this is related
to the lossy-ness of the exchange points and certain providers in 
particular. 

So, the multi-part question I need answered goes something like this:

1)  Is it possible to "multi-home" on the Mbone.

2)  If 1) is possible, how do I prevent from being a "transit provider"
for Sprint and my other feed (Either my provider or one or more of their
upstreams uunet and mci).

3)  If 1) isn't possible, what other options do I have when I end up with
a lossy feed which makes the already-bad nanog audio impossible to listen
to?

For your reference, our primary tunnel endpoint is a Cisco router running
bleeding-edge "standard release" IOS.  11.2(??)

Thanks for any help and/or pointers.

[email-masked]

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From: Bill Fenner <[email-masked]>
Date: Fri, 7 Nov 1997 13:54:25 PST

>1)  Is it possible to "multi-home" on the Mbone.

Yes, although you have to be careful about transit.

>upstreams uunet and mci).

mrouted 3.9 has a "notransit" flag; routes learned on an interface marked
"notransit" are not advertised out other interfaces marked "notransit".

With IOS, presumably you can experiment with the "ip dvmrp metric" command;
perhaps "ip dvmrp metric 32 list <something> dvmrp", to prevent advertisement
of any routes except the ones belonging to you, where access-list <something>
denys your routes but permits all others.

  Bill

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From: Dino Farinacci <[email-masked]>
Date: Fri, 7 Nov 1997 14:25:24 -0800 (PST)

>> denys your routes but permits all others.

    The precise syntax on a tunnel would be:

	interface tunnel0
	ip dvmrp metric 0
	ip dvmrp metric 0 dvmrp

Dino

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From: Dino Farinacci <[email-masked]>
Date: Fri, 7 Nov 1997 15:07:59 -0800 (PST)

>>     The precise syntax on a tunnel would be:

    You probably want:

	interface tunnel0
	ip dvmrp metric 0 dvmrp

    if you want your own (network number) routes to be sent. If you want to
    tailor them, you should use:

 	interface tunnel0
 	ip dvmrp metric 1 list <acl>
 	ip dvmrp metric 0 dvmrp

Dino