group multicast from ethernet to wifi

RouterOS General
1

Hello,

I have a MikroTik RB951G-2HnD that I am using just as a switch (no NAT,DHCP…) + WiFi AP. Then I have a device that sends UDP multicast messages to IP “224.0.XX.XX”. That device is connected directly to the MikroTik by ethernet.

I have two other PCs on the same subnet connected to the same MikroTik - one connected by ethernet, one by WiFi. The ethernet one is receiving these multicast messages, the wifi one is not. Why?

In MikroTik, WAN + Ethernets are all bridged. Broadcasting (for example tried 192.168.1.255) from eth to wifi works fine. Tried IGMP snooping on/off but no change.

I found that it has something to do with IGMP and that in order for devices to be able to receive multicasted messages, they have to register to the particular IGMP group (for example 224.0.0.5). However in my case, there is no software on neither of my PCc (ethernet + wifi) that should listen and register to that particular group. And yet I can get the messages on the ethernet one, but not on the other wifi one.

Is this normal behaviour? Can it be restricted by some packet flags that it should not be sent over WiFi?

2

Set multicast-helper=full on wireless interface. You can read more about what id does in wireles manual. The problem is in packet timing and wireless devices going to sleep when idle …

And make sure basic rate of wireless AP is larger than multicast data rate.

The two options above are not actually related, either one should solve the problem … the former offers more reliable way and mostly also allows better wifi AP performance.

3

yes, setting the multicast-helper to full helped, thank you very much :slight_smile: didn’t think it will be that easy.