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New Member

3548 multicast problem

my core switch is C4006

and edge switch are 3548 switch and 2950 T-24

when I implement multicast Service , the 2950T-24 seems normal

but the 3548 switch seems slowly ,

I have enabled CGMP on C4006 and 3548 switch (include fast leaving )

Why ??

3 REPLIES

Re: 3548 multicast problem

Hi,

are you sure your CGMP is working correctly, i.e. the multicast frames are delivered only to the proper ports, not to all ports on 3548?

Regards,

Milan

New Member

Re: 3548 multicast problem

Hello

Thank you for your help , but i do not understand what you mean

i config my 3548 only CGMP enable and CGMP fast leave

Is it correct ??

Re: 3548 multicast problem

Hi,

that was not enough.

When a PC is joining a multicast group it sends out a IGMP join message. Unfortunately 3548s don't provide IGMP snooping feature.

Cisco is using proprietary CGMP protocol to fix this issue. But it requires a router to "translate" IGMP to CGMP and send the info to the switch.

See

http://www.cisco.com/warp/public/473/22.html

and especially

http://www.cisco.com/warp/public/473/38.html

for details.

These articles are about CatOS switches but configuring IOS switches ie even easier - CGMP is enabled by default.

If you configure switches and router correctly multicasts are sent from the source only to the ports on which multicast group members are connected.

If CGMP doesn't work correctly in your network multicast frames are flooded to all ports on the switch.

You can easily test it: connect a protocol analyser to a port on the switch, start a multicast session (I suppose you are using some application which sends multicasts to clients) and see if multicasts are coming to the analyzer. If yes, CGMP is not working correctly.

Regards,

Milan

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