IGMP multicast over wireless interface

RouterOS Wireless Networking
1

Wonder if anyone has experience on this & can advise me:

Assume I have an MT-powered AP, and say 10 remote CPEs (also MT powered) with atheros wireless interfaces.

2 or more of PC clients behind the CPEs want to associate to an IGMP multicast which is being broadcast from behind the AP.
What happens across the wireless interface? Do the packets get sent out twice, or what?

I’m assuming the AP has the interfaces bridged, and using WDS through to the CPEs. Do routed configurations make any difference in this application?

Regards

2

Multicast is always treated as broadcast by anyone who does not speak IGMP on ethernet. At least it should otherwise it would not be correct.

If those ten CPE’s are WDS bridged then 10 copies are sent as that would result in 10 virtual interfaces. It does not matter that they are not listening as i dont think RouterOS runs IGMP listening/snooping.

3

Thanks Sten,

Is there any way round this, i.e. avoid up to 10 copies of the data being sent across the wireless interface?

We have a potentially large project that would really benefit from this

Regards

4

Not with WDS unless RouterOS supported IGMP snooping.

5

Thanks Sten,

What about a routed setup? Any other configs that might help?
(sorry I am not a complete router-wizard … yet)

Regards

6

If you dont run WDS you would only have one copy sent without re-transmissions at basic rate. Then the cpe must forward these multicasts and each end-user would receive a copy regardless. Perhaps you could accomplish something with bridge nat?

7

Last time i checked RouterOS does not support IP multicast properly yet.
I’m not multicast wizard. If anyone knows how to route multicasts with routeros for proper multicast routing then please let me know. I guess theoretically one could do static multipath routing together with ARP trickery to do one way multicasts… Don’t know if that would be accepted by transmitter or receiver.