[c-nsp] Multicast Issue

Wed Apr 26 20:09:13 EDT 2006

At 04:14 PM 4/26/2006, John Neiberger pronounced:
>I think you're right that the problem is at L2. The 6513 is connected
>via trunk port to a 2950. I have IGMP snooping disabled on the 2950 and
>another static MAC address entry pointing to the interface where the
>server is connected. It sure seems like it should work, darn it!  :)
>
>Regarding snooping on Vlan4, I didn't disable it globally but I did
>disable for that MAC address using the disable-snooping keyword in the
>mac-address-table command.

This would be on a per vlan basis though. Eg, if you did it in vlan 1 
& not in vlan 4, it would not apply to vlan 4.

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.

Tim

>Thanks!
>John
>--
>
> >>> Tim Stevenson <tstevens at cisco.com> 4/26/06 5:05:11 PM >>>
>I assume you never disabled snooping in vlan 4? Multicast router
>ports (in this case the internal router, the RP/MSFC) are always
>member ports for all snooping groups.
>
>This all looks ok.
>
>Can you do a sh mls ip multicast and see if the packet stats increase
>for this S,G - if they do (& I think they will/should), then the
>packets are getting to vlan 1 & then you need to focus your
>troubleshooting on L2 between vlan 1 & the server.
>
>Tim
>
>At 03:58 PM 4/26/2006, John Neiberger pronounced:
> >This is on a native mode SUP2.
> >
> >I just had my co-worker startup the client and I see this:
> >
> >(10.a.b.c, 224.0.1.55), 00:07:16/00:00:10, flags: T
> >   Incoming interface: Vlan4, RPF nbr 0.0.0.0, RPF-MFD
> >   Outgoing interface list:
> >     Vlan1, Forward/Dense, 00:07:16/00:00:00, H
> >
> >where 10.a.b.c is the IP address of the client.
> >
> >Here is the output of some debugging:
> >
> >y19w: IP: s=10.a.b.c (Vlan4) d=224.0.1.55 (Vlan1) len 92, mforward
> >1y19w: MRT: Create (10.a.b.c,224.0.1.55), RPF Vlan4/0.0.0.0
> >1y19w: MRT: WAVL Insert interface: Vlan1 in (10.a.b.c,224.0.1.55)
> >Successful
> >1y19w: MRT: Add Vlan1/224.0.1.55 to the olist of (10.a.b.c,
> >224.0.1.55), Forward state
> >1y19w: IP: MAC sa=0003.470b.6bce (Vlan4), IP last-hop=10.a.b.c
> >1y19w: IP: IP tos=0x0, len=78, id=0x34BF, ttl=1, prot=17
> >1y19w: IP: s=10.a.b.c (Vlan4) d=224.0.1.55 (Vlan1) len 92, mforward
> >
> >Interestingly, the output of show mac-address-table multicast shows
>two
> >entries for 0100.5e00.0137:
> >
> >4  0100.5e00.0137    static  Yes   --  Router
> >1  0100.5e00.0137    static  Yes   --  Gi4/16
> >
> >The Vlan1 entry is my static entry. Why would the 6513 an entry in
> >Vlan4? The source of the packet is in Vlan4 but I don't understand
>why
> >that would create an entry in the mac address table. Isn't the table
> >only for destination MAC addresses? If so, why would an entry show up
> >for the source?
> >
> >Thanks!
> >John
> >--
> >
> >
> > >>> Tim Stevenson <tstevens at cisco.com> 4/26/06 4:44:38 PM >>>
> >Do you see a source,group entry? You seem to be running dense mode,
> >and DM fwding is always on the s,g never the *,g (the *,g is created
> >but not used for fwding).
> >
> >So you need to see a PC,224.0.1.55 mroute entry with vlan1 as an OIF.
> >
> >BTW, what supervisor engine are you using, sup2 or sup720?
> >
> >Also, you are sure the packets are not getting L3 switched (ie, that
> >they're not dropping somewhere in vlan 1)?
> >
> >Tim
> >
> >At 02:37 PM 4/26/2006, John Neiberger pronounced:
> > >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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> > >https://puck.nether.net/mailman/listinfo/cisco-nsp
> > >archive at http://puck.nether.net/pipermail/cisco-nsp/
> >
> >
> >
> >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
> >********************************************************
> >The contents of this message may be *Cisco Confidential*
> >and are intended for the specified recipients only.
>
>
>
>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
>********************************************************
>The contents of this message may be *Cisco Confidential*
>and are intended for the specified recipients only.

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
********************************************************
The contents of this message may be *Cisco Confidential*
and are intended for the specified recipients only.