[c-nsp] Multicast Issue

[Marko Milivojevic]

The only thing that comes to my mind is that 2950 has IGMP snooping enabled. 
In that case, it won't forward traffic out its interfaces if it doesn't see 
joins. Have you tried disabling IGMP snooping on it? This will make the 
switch flood multicast traffic (with all the side effects of this).

Marko.

John Neiberger wrote:
> I've got an interesting issue that I think I'm tantalizingly close to
> solving but I haven't had to deal with multicast stuff in years.
> 
> We have a PC on one subnet that is sourcing a multicast packet. I need
> to get that packet to a device on another LAN that is not capable of
> sending IGMP joins. Here's the topology:
> 
> PC *- 6513(IOS) *- 2950 *- Server
> 
> In this case, the PC is sending out a single multicast packet trying to
> reach the server. The packet does not reach the server because it can't
> join the group. The multicast group is 224.0.1.55. The "server" is in
> Vlan1, so on the 6513 I have the following configured:
> 
> int Vlan1
>  ...
>  ip igmp static-group 224.0.1.55
> !
> ! That makes Vlan1 show up in the mroute table, but I still need to
> forward that packet out some particular interface, right? So...
> !
> mac-address-table static 0100.5e00.0137 vlan 1 interface
> GigabitEthernet4/16
> !
> !  That statically forwards traffic destined for that multicast address
> out the interface leading to the Catalyst 2950
> 
> On the 2950 I have the following:
> 
> mac-address-table static 0100.5e00.0137 vlan 1 interface
> GigabitEthernet0/2 
> 
> That should forward the multicast traffic to the server hanging of off
> g0/2. However, this isn't working. I've tinkered with a couple of
> different configs but nothing seems to work. Debugging shows that the
> multicast packet is making it to the 6513.
> 
> 1y19w: IP: s=10.a.b.c (Vlan4) d=224.0.1.55 (Vlan1) len 92, mforward
> 
> The output of "show ip mroute 224.0.1.55" shows the following:
> 
> (*, 224.0.1.55), 00:00:01/00:02:58, RP 0.0.0.0, flags: DC
>   Incoming interface: Null, RPF nbr 0.0.0.0
>   Outgoing interface list:
>     Vlan1, Forward/Dense, 00:00:01/00:00:00
> 
> It looks to me like the 6513 should know where to forward the packets
> but it isn't working. 
> 
> Any ideas?
> 
> Thanks!
> John
> --
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