At 07:27 PM 2/6/02, s vermill wrote: >Hello all, > >I am studying multicast technologies for acedemic reasons and also so that I >can hopefully resolve a real-world issue. I have been reading about CGMP in >various Cisco Press books, CCO - all the usual suspects. Seems that all of >the examples show a switch directly connected to a router. Is it just a >foregone conclusion that a Catalyst switch with an on-board route processor >will be the architecture?
No. It could be a "real" router that is configured for CGMP. >Because I was thinking of the typical switch >block. You have your distribution layer switch (hopefully L3 capable) and >also a bunch of downstream access layer switches. If a switch were stacked >below an upstream access layer switch instead of being directly connected to >distribution, I guess CGMP would break? I don't think it would break, although there are definitely many cases where it does break. Is this sort of what you have in mind? Router (or distribution switch with router blade) | | Access switch with CGMP | | Access switch with CGMP | | multicast recipients > A host on the lowest switch in the >stack might send an ICMP join. When the router sends the CGMP message to >the all-switch multicast, the higher layer access switch wouldn't have the >MAC address of that host stored. That's where I would disagree with you. Switches need to store all MAC addresses that they can get to, not just the ones that are directly connected. I think the higher-layer switch would have the MAC address of the multicast recipient that sent the IGMP join (at least if you were using my simple topology.) My concern is more with the CGMP message to all switches. Do switches forward these? They must. Well, it's time to get off the computer for tonight! :-) Talk to you tomorrow, Priscilla > So it wouldn't forward the multicast frame >on any of its ports? Or is it sent along all trunk ports by default? > >I sense that I have lost sight of the big picture. > >Many thanks, > >Scott ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=34718&t=34704 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
