RFC4541 section 2.1.2 explains link local multicast data forwarding rules for IGMP snooping
Cheers, Adam Booth > On 10 Oct 2013, at 6:28 pm, Matt McAdory <[email protected]> wrote: > > There is a problem with mcast MAC collisions. I'd bet that IGMP snooping > goes further into the frame than you think. Also the 3560 references IPs > not MACs for group differentiation. > > I suspect that your question is answered in the following quote from the > below doc: > > "*The switch supports IP multicast group-based bridging, rather than > MAC-addressed based groups*. With multicast MAC address-based groups, if an > IP address being configured translates (aliases) to a previously configured > MAC address or *to any reserved multicast MAC addresses (in the range > 224.0.0.xxx)*, the command fails. Because the switch uses IP multicast > groups, there are no address aliasing issues." > > I suspect that additional detail is proprietary and may require Super-duper > Top-Secret G14 level clearance to get more specifics. > > http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_52_se/configuration/guide/swigmp.html#wp1027678 > > MMc > > Matt > > > On Wed, Oct 9, 2013 at 11:36 PM, Andres Villalva <[email protected]>wrote: > >> Hi all, >> >> I am trying to find out how "IGMP snooping does not constrain Layer 2 >> multicasts generated by routing protocols." >> >> What is the mechanism by which switches are able to say "yes, you are >> routing traffic - IGMP snooping rules don't apply" given that they are >> limited to reading L2 headers? >> >> I understand the multicast IP to MAC translation but the last 23 bits of an >> IP address does not cover the critical first octet (224), hence, in my eyes >> the switch still has no way of knowing whether the packet is a routing >> protocol or not? >> >> Thanks for your help, >> Andres >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> Are you a CCNP or CCIE and looking for a job? Check out >> www.PlatinumPlacement.com >> >> http://onlinestudylist.com/mailman/listinfo/ccie_rs > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
