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New Member

Multicast problem on cat6509 ,help plz!

I 'm implementing multicast over cat 6509 , but I encounter a problem is very confused me .I enabled Ip multicast-routing and ip pim spare-mode ,igmp-snooping on a vlan interface . Then I test a multicast server .

The video is always paused and buffered.( The server and client is in same vlan and connect to 6509 directly ) Then I connect them using a hub. The video is very smooth.I don' t know what config is needful.I already refered to


but they're helpless , pls help me , any advice is very appreciated !

regard ,


New Member

Re: Multicast problem on cat6509 ,help plz!

If your server and client are on the same VLAN you don't need to enable multicast on the switch. If you remove any multicast configurations and ensure the port setting are set correctly on all devices (server, client, switch are either hard set to speed/duplex or auto on both sides), you should have the same performance as your hub. You problem sounds like a NIC setting mismatch.

In any case, to enable multicast between two VLANs on a 6509...

You only need a simple config in your MSFC of

interface vlan 1

ip pim sparse-dense-mode

ip cgmp


interface vlan 2

ip pim sparse-dense-mode

ip cgmp

on the switch enable "set cgmp enable"

New Member

Re: Multicast problem on cat6509 ,help plz!

What module are you using on the catalyst 6500 ? Is it a ws-x6248-rj45 ?

There is a problem with the buffer size on the ws-x6248-rj45. So if your UDP segments are large then it could be the problem. Try the command set options flowcontrol enable all. This will not affect the switch if you don't have any ws-x6248rj45 cards.

If you have the switch server and clients on the same vlan then you definitely don't need to enable multicast routing at all. And remember, if you enable sparse-dense mode then you will need to put an rendenzour point somewhere on the network.

But I believe your problem is more simplier than that. Check the couters for drops or discards. If you are seeing discards then it means the ports may be running out of buffers. And if you are running the ws-x6248 modules then my command may be able to help you out.

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