[c-nsp] Ignoring / limiting 239.255/16

[Phil Mayers]

We've got a lot of winXP boxes on-net which join the UPnP groups and the
multicast routing table is filled with useless entries.

Given that we don't have access lists at layer2, what is the best way of
preventing out routers:

 a. processing the IGMP joins
 b. forwarding the packets

The network is 6500s running SXF6 (and upwards). If it matters (it
shouldn't, I suspect) the networks are VRFs using MPLS and MVPN.

I suspect a combination of "ip igmp access-list" and "ip multicast
boundary" would help, but I'm not sure on the syntax.

Also - is it *strictly* legal to limit these addresses to the local
subnet?