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
