Multicast activity on switches

[gerardsweeney]

Hello, all..

 

(If this is in the wrong category, hopefully some kind soul will move it)

 

 

This may sound like a strange query, but bear with me!!

 

When you have a multicast stream from either imaging (in our case, Altiris but whatever your preference), or something like Exterity..

 

On the network switches - should it just be the ports of the sender/recipients which go like strobe lights?

 

The reason I ask is that in 2 of my schools that I've looked at, if we have a multicast stream broadcasting from a PC on VLAN 1, then ALL the ports on that VLAN on ALL of the Cisco switches in the cabinet (possibly the school? I'm in a single cabinet location here) turn into strobe lights. Ports which are on VLAN2 stay at their normal blink rate.

 

I thought it should only be the ones actually receiving the multicast (and the one doing the broadcast) that should show heavy activity (strobe lights), while the others should remain at the normal blink rate. This "all turn into a strobe" sounds like flooding? (but what the heck do I know?)

 

 

These are a mix of Cisco 2950, 2960, and 3560.

 

I'm not a network/infastructure bod, as you can probably tell!!

 

 

Thoughts/opinions gratefully received.

 

Cheers,

Gerard

[DMcCoy]

Enable igmp snooping on the relevant vlans on each switch. It won't multicast to another vlan without some multicast routing enabled (which is usually turned off).

[finbar33]

DMcCoy is right ip igmp will help, but can you post your config of the switches which would help to understand the problem and might help find a answer.