Re: cgmp leave

whanson · ‎04-23-2004

Can someone explain to me how enabling cgmp leave over having it disabled works.

mvalentine · ‎04-23-2004

with cgmp leave enabled the switch detects IGMPv2 messages sent toward the router, it then starts a timer and sends a message out the port the igmp leave was recieved on if it doesn't here back by the time the timer expires it prunes the port. If it is the last port in the group it sends the igmp leave up toward the router for the router to process.

without cgmp leave enabled the switch doesn't prune any ports until their are no recivers left for that group.

you should check which version of igmp your hosts are using because IGMPv1 doesn't send a leave message so cgmp leave is useless in your switch. with IGMPv2 they do send a leave so cgmp leave might make sense for you

whanson · ‎04-27-2004

Hi, thanks for the info. Maybe you can help me understand something that I'm scratching my head over. We have a customer that runs a video application through a box called the VBRICK. The network orginally had a cat 4000 with layer 3 and downstream gig to cat 2950s. The vbricks run at 10 meg ethernet and were killing each other until they were configured for join own multicast group. Secondly, we had to move the vbricks to a 3524 running CGMP because a curious problem with the cat 2950 where it builds its pruning tables and then flushes them out periodically. This caused no end problems for the 10 meg vbricks until we moved them to the cat 3524. So far so good. So we have vbricks on the 3524 uplinked gig to the 4000 and then gig links to cat 2950s which do not support CGMP only IGMP snooping. Customer still complained of performance on the network and then CGMP leave introduced on the cat 3524 and customer says problems disappeared. How can this be if all the cgmp leave does is stop the flow upstream from the cat 3524 to the cat 4000

mvalentine · ‎04-28-2004

Are all these deives on the same vlan? Is the vbrick the multicast sender and the customers on the 2950 the recievers. If the 4000 is layer 3 are you running pim sparse mode, dense mode or sparse-dense?

whanson · ‎05-11-2004

yes, all devices on the same vlan. 4000 is layer 3 running spare-dense.