When a multicast reciever wishes to recieve multicast traffic it must send an IGMP join for the multicast group. CGMP/IGMP snooping get in the way of this and makes sure the stream only goes to needed ports. A multicast sender doesn't need to send an IGMP join to the router to start sending multicasts (that can't be a requirement, because if it was what would happen on multicast networks without routers?) A sender simply starts sending packets. Because a sender doesn't send IGMP joins CGMP and IGMP snooping cannot function. Kinda sucks huh?
If your intrested I'm working on an open source multicast project that simulates multicast traffic at http://sourceforge.net/projects/mc-mint/ If you want you can look at the souce and you'll see the sender function doesn't use IGMP joins. Mike ------------------- Mike Bernico [EMAIL PROTECTED] Illinois Century Network http://www.illinois.net (217) 557-6555 > -----Original Message----- > From: Fears Michael S SSgt 50 CS/SCBBN > [mailto:[EMAIL PROTECTED]] > Sent: Friday, February 01, 2002 7:58 AM > To: [EMAIL PROTECTED] > Subject: RE: multicast / CGMP towards the multicast server [7:33964] > > > Nigel, Thanks, Yes the switch and users are all on the same > VLAN. PIM and > IGMP > are working fine across the router and into other CGMP enable > switches. > The thing I was not sure of, was: if I have a server multicasting > on the same switch/VLAN as other users, can I prevent the multicast > stream from flooding the broadcast domain that the server is in? > > I was asked this question and my answer was "no". I thought > it was just poor > design > to have the multicast server on the same VLAN as the users > who are not using > it. > > Maybe I'm wrong?? > > > > > > -----Original Message----- > From: Nigel Taylor [mailto:[EMAIL PROTECTED]] > Sent: Thursday, January 31, 2002 8:19 PM > To: [EMAIL PROTECTED] > Subject: Re: multicast / CGMP towards the multicast server [7:33964] > > > Michael, > Of course this would depend on if the multicast > server and the > host connected on the same switch was assigned to the same > vlan(broadcast > domain). Just some quick points to mention.. > > Routers by default will not forward multicast traffic. > However, if you > enabled a multicast routing protocol(PIM, DVMRP) then this is > possible. The > important thing here is that IGMP is used by hosts to inform > routers of > their intent to become part of a multicast stream. This > depends on your > implementation of the multicast protocol. IGMPv2 has been improved to > support leaves from a multicast group which is not supported > in IGMPv1. > This way the host is able to notify the source of it's intent > to leave the > multicast group. This is will allow the routers to prune the > multicast > traffic from the segment removing the unnecessary traffic, > providing no > other host on the segment remains a member of the multicast stream > > A good title as recommended by a number of folks on the list > is Developing > IP Multicast Networks > Author: Beau Williamson. ISBN: 157870779 > > HTH > > Nigel > > > > ---- Original Message ----- > From: "Fears Michael S SSgt 50 CS/SCBBN" > To: > Sent: Thursday, January 31, 2002 4:59 PM > Subject: multicast / CGMP towards the multicast server [7:33964] > > > > If a multicast server is connected to a Cisco Switch > running CGMP, and > > several hosts are connected to the same switch, will a > router turn off the > > switch ports for the users that are not requesting the multicast? > > > > So, will CGMP work back towards the multicast server? > > > > Fears Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=34061&t=33964 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
