[c-nsp] BGP v4 multicast

Gert Doering gert at greenie.muc.de
Wed Oct 1 12:22:45 EDT 2008


On Wed, Oct 01, 2008 at 05:17:42PM +0100, Phil Mayers wrote:
> >Same way you currently do it with IPv4 unicast, just put the statements
> >under "ipv4 multicast".
> >
> >As in - if you're doing "redistribute static route-map foo", you can
> >just put the same statement under "address-fam ipv4 multicast" as well.
> Ok, that's what I wasn't clear on - whether the "v4 multi" AF would read 
> the normal unicast routing table, or whether it required "ip mroute" 
> statements to Null0 or something vile.

Ah.  That was the issue :) - no, it doesn't, at least on on IOS (XR might
be different).

> >>Is this recommended?
> >
> >Well, we have just removed all IPv4 multicast BGP from our network, since
> >it doesn't work on "the global Internet" :-) - but technically, use 
> >whatever
> Interesting; does that mean you have abandoned ASM and are pushing SSM, 
> or abandoned multicast completely (although given the lack of 
> SSM-enabled apps, they may be one and the same)

We have, for the time being, abandoned cross-provider multicast completely.

> Sadly I am stuck supporting use of the "wonderful" AccessGrid 
> technologies (sigh) which more or less mandate multicast.

Oh, well, if anybody actually starts *using* IPv4 multicast, it might
return to a more or less working state.

Our problem was that, since it is hardly ever used, providers tend to
break it during network changes ("forget to turn on PIM on newly enabled
circuits", and things like this) - and when people notice that it's broken,
it's 4 weeks later, and nobody remembers that there was a "recent" change...

So debugging always was very painful, and had no relation to the amount
of users...

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de

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