[c-nsp] Multicast Issue

[Tim Stevenson]

Static multicast MAC entries override IGMP snooping.

If there is an S,G then you can see if the OIF has the H flag (h/w 
switched) and you can see stats for it with sh mls ip multicast.

Tim

At 03:43 PM 4/26/2006, John Neiberger pronounced:
>Yes, I've disabled IGMP Snooping. I would have thought that that would
>allow this setup to work. I know I must be close but whatever is wrong
>is eluding me.
>
>Thanks,
>John
>--
>
> >>> Marko Milivojevic <markom at PanGalactic.net> 4/26/06 4:33:57 PM >>>
>
>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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> >
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Technical Marketing Engineer, Catalyst 6500
Cisco Systems, http://www.cisco.com
IP Phone: 408-526-6759
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