I think if you have a router upstream configured for PIM you won't need to configure the switch as the querier
On Sun, Apr 11, 2010 at 4:07 PM, <christopher.mar...@usc-bt.com> wrote: > Said Vince: > > On the C3560, with default config, i believe igmp snooping is enabled > > by default. A multicast source floods all traffic to all ports in the > > vlan, until I configure 'ip igmp snooping querier' at which point the > > flooding stops. I would have expected igmp snooping to figure out that > no > > receiver requested traffic, so no flooding should never occur at all ? > > The behavior you describe sounds correct. IGMP snooping depends on IGMP > traffic in order to have something to snoop. Without an IGMP querier, you > can only count on the initial (unsolicited) IGMP host report. There might > be no other traffic, rendering IGMP snooping is totally helpless. It makes > sense that traffic would flood to all ports until you enable a querier. > This sounds like a feature: The switch is smart enough to disable > multicast filtering when the information required for good decision-making > isn't available. > > > If I remove 'ip igmp snooping querier', and configure 'ip pim sparse- > > mode' on an SVI in that vlan, again I would expect the 3560 to stop the > > flooding, but the flooding goes on an on, which i dont expect. > > Is 'ip multicast routing' enabled? What does 'sho ip igmp snooping > querier' have to say about it? > > > On the 4948, flooding again does occurs with default config with igmp > > snooping enabled by default, but different to the c3560 both 'ip igmp > > snooping querier' and/or 'ip pim sparse-mode' take care of controlling > > that. > > Last time I needed 'ip igmp snooping querier', it wasn't available on the > 4948. What version are you running? > > > am i getting it wrong, or is it indeed by design that the boxes behave > > differently ? > > It could be different defaults (or manual configuration) around enabling L3 > multicast. Without 'ip multicast routing', 'ip pim sparse=mode' is a no-op. > > Good luck. > > /chris > > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/