vlan and multicast

homework time?

IGMP is about devices telling the local router interface what groups they want.

multicast routing is then needed to pass multicast packets between them

So - not unless there is a L3 box somewhere to act as a multicast router (which is probably what would handle the IGMP stuff).

and on some Cisco boxes multicast requires an additional licence - eg if the VLAN switch is a Cat 3560 / 3750 then it will need whatever Cisco are calling an enhanced image this week.

er - it doesnt work unless you add more functionality?

not if they dont pass thru a NAT function :)

If yes how to identify the source of the multicast once gone

not really, I plan to buy a used ethernet switch that could deals with vlan (port based) and IGMP but I prefer to be sure I will the get what I need. On 2 different VLAN, I have two stations with USB webcam that multicast video stream. I want to monitor these streams from a 3rd vlan. Because a VLAN define a broadcast domain, I was thinking that if the port where the monitoring station is connected could be in several VLANs (1 2 and 3) at the same time, it could receive stream of vlan 1 after IGMP registration and/or stream from VLAN 2 after another IGMP registration. Adding a layer 3 box may be more expensive.

Thanks for your help.