[c-nsp] igmp snooping inside 802.1q trunks

[Tim Stevenson]

Not sure what to conclude based on that information.

Flooding will happen in a few cases that occur to me:
* IGMP snooping disabled
* the port is learned/configured as a mrouter port
* no querier present in the vlan (you can get unpredictable behavior 
here, snooping is not supported unless there is a querier)
* the group IP maps to a reserved range MAC (0100.5e00.00xx)
* a new source starts sending & no group mac exists (need to install 
a "source-only" entry - this flooding lasts a very short time)
* a source-only entry is removed from the h/w but the source is still 
sending (again, flooding for a very short time)

The fact that the streams originate from any particular switch (with 
or without the querier attached) should not make any difference that 
I can think of unless it falls into the above categories.

A TAC case is probably the quickest way to resolution here...

Tim

At 11:02 AM 2/1/2006, Vladimir Ivashchenko submitted:

>I traced multicast streams that were being sent to trunks without
>receivers and found that they were coming from a different switch than
>the querier. Is flooding expected in such cases?
>
> > Are you seeing snooping entries for the MAC? 0100.5e40.00xx (sh mac-
> > multi igmp) If so, what is the port mask? You are sure it is
> > 239.192.0.x & not 239.128.0.x? The latter would map to a reserved
> > range MAC, & we won't install a snooping mac entry for it, it will
> > flood....
> >
> > Tim
> >
> > At 10:19 AM 1/31/2006, Vladimir Ivashchenko submitted:
> >
> > >239.192.0.x
> > >
> > >On Mon, 2006-01-30 at 13:40 -0800, Tim Stevenson wrote:
> > > > What group(s) are you sending to?
> > > >
> > > > Tim
> > > >
> > > > At 01:28 PM 1/30/2006, Vladimir Ivashchenko murmered:
> > > > > > > The problem is that 6500 seems to unconditionally forward
> > > all multicast
> > > > > > > traffic to all trunk ports even if there are no receivers
> > > > > > > there. E.g. "show mac-address-table multicast" does not show
> > > > > > > any entries for that port, however it still receives all
> > > > > > > multicast traffic.
> > > > > > >
> > > > > > > Any ideas?
> > > > > >
> > > > > > The 6500 is going to forward multicast traffic to any routers it
> >
> > > > > > learns about. Does a "show multicast router" on the 6500 list
> > > > > > all the trunk ports?
> > > > >
> > > > >I checked it (using IOS's sh ip igmp snooping mrouter), only one
> > > > >port there as expected.
> > > > >
> > > > >--
> > > > >Best Regards
> > > > >Vladimir Ivashchenko
> > > > >Chief Technology Officer
> > > > >Thunderworx, Cyprus - www.thunderworx.com
> > > > >_______________________________________________
> > > > >cisco-nsp mailing list  cisco-nsp at puck.nether.net
> > > > >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.
> > >--
> > >Best Regards,
> > >Vladimir Ivashchenko
> > >Chief Technology Officer
> > >Thunderworx Cyprus - www.thunderworx.com
> >
> >
> >
> > 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.
> > _______________________________________________
> > cisco-nsp mailing list  cisco-nsp at puck.nether.net
> > https://puck.nether.net/mailman/listinfo/cisco-nsp
> > archive at http://puck.nether.net/pipermail/cisco-nsp/
>--
>Best Regards,
>Vladimir Ivashchenko
>Chief Technology Officer
>Thunderworx Cyprus - www.thunderworx.com



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.