All things related to multicast

[Tsegreda Beyene <>]

At 12:19 PM 11/12/2002 -0500, Wallace, Steven S wrote:
> I defer to Tsege.  I have to say that this is VERY odd.  Turning off
> IGMP snooping turns off ASIC forwarding?

If you turn it off, you disable hardware switching of multicast traffic, 
not unicast traffic...just making sure this is clear.
http://www/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a008007e6e1.html#xtocid9

PFC1, PFC2, and the DFCs all use the Layer 2 multicast forwarding table to 
determine on which ports Layer 2 multicast traffic should be forwarded (if 
any). The multicast forwarding table entries are populated in conjunction 
with Internet Group Management Protocol (IGMP) snooping (see "Configuring 
IGMP Snooping").

Tsege


> ssw
>
> -----Original Message-----
> From: Tsegreda Beyene 
> [mailto:]
> Sent: Tuesday, November 12, 2002 11:58 AM
> To: Wallace, Steven S; Alan Crosswell; 
>
> Subject: RE: Catalyst RGMP?
>
> At 02:00 PM 11/11/2002 -0500, Wallace, Steven S wrote:
> >I would tend to disagree.  If there are only routers connected to the
> >6509s, I would think that IGMP snooping should be turned off.
>
> Steve,  You should always turn on IGMP snooping on a 6500..
> if you do not, then you are disabling the ASIC switching...
> That is the implementation of the 6500.
>
> Tsege
>
> >   Turning
> >IGMP snooping on is going to just exercise the code that's looking for
> >IGMP host reports (non of which will be coming from the routers).  I
> >understood RGMP to be Cisco proprietary solution to the problem you
> >describe, although I've never tried it.  Having IGMP and RGMP turned
> off
> >should work just fine, although you will be flooding some of the
> >multicast traffic down links with no downstream listeners (which may be
> >just fine if that doesn't cause congestion).
> >
> >Steven Wallace
> >
> > > -----Original Message-----
> > > From: Tsegreda Beyene 
> [mailto:]
> > > Sent: Friday, November 08, 2002 3:34 PM
> > > To: Alan Crosswell; 
>
> > > Subject: Re: Catalyst RGMP?
> > >
> > > Hi Alan,
> > >
> > > comment inline please:
> > >
> > > At 02:26 PM 11/8/2002 -0500, Alan Crosswell wrote:
> > > >Anybody have experience with this?  Is this what I want to use in
> >lieu
> > > >of the ability to do PIM snooping?
> > >
> > > No. Cisco does not do PIM snooping.
> > >
> > > >I have a dual-star L2 topology using
> > > Not that this will not work..I prefer point-to-point as opposed to
> >dual
> > > star.
> > >
> > > >Catalyst 6509 switches which my routers are each connected to.
> Right
> > > >now I have IGMP snooping disabled
> > >
> > > You should always enable IGMP snooping on the 6500..If you disable
> it
> > > you are basically disabling hardware switching.
> > >
> > > >on these switches since it seemed to
> > > >interfere with multicast connectivity and didn't make sense since
> the
> > > >only devices on the switch are routers so the only IGMP to snoop
> >would be
> > > >router advertisements.
> > > >
> > > >Maybe I should just not touch anything.  It's sort of working
> >today:-)
> > >
> > > I will forward your e-mail to appropriate people and they will help
> >you
> > > out.
> > >
> > > Thanks.
> > >
> > > Best Regards,
> > >
> > > Tsege
> > >
> > > >/a