[c-nsp] Multicast Issue

[John Neiberger]

>In any case, the tools to use now would be sh int cou on gig 4/16 to 
>see if mcast out is incrementing on the 6k (hopefully it's a fairly 
>high rate source, if not, then you won't be able to tell), and if 
>mcast in is incrementing on the 2950.
>
>You can also always try a span session to a sniffer of gig 4/16 in 
>the tx direction to see if the packets are going out.

Unfortunately, this application sends a single multicast packet. It
will send up to six if there is no response. This is just a horribly
designed application. Get this:

The client begins talking to the server via TCP, so it already
obviously knows the server's IP address. After it's been talking to the
server for a few seconds (a couple hundred packets) the client sends a
single multicast packet to 224.0.1.55. This is some sort of server
location mechanism. But it shouldn't be necessary because the client
obviously already knows the IP address of the server. To make this even
more colossally dumb, the IP address of the server is IN THE DATA
PORTION OF THE MULTICAST PACKET! If the client does not receive a
unicast response to this multicast packet, the client can't connect, at
least from the user's perspective. Really bad design because that means
that the server doesn't use IGMP to join the group, which means it has
to be on the same LAN as all of the clients. I'm just trying to find a
way to make it work for now until we can talk to the developers of the
application.

Thanks!
John
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