Hello,
I recently got a GL-SFT1200. I Set it Up as WiFi extender to my Router. Topology is: deviceA - sft1200 - Router - deviceB
I want to Multicast from deviceB. Unfortunately, deviceA ist Not Receiving the packages. Vice verca is working, but this does Not Help me. I found the Option to activate igmp snooping, but this didnt Help. My application ist a very simple audio broadcasting application.
Any Help is appreciated.
Kind regards!
Hi,
Can you tell me how you test that it not works?
What i also want to know is, how does device B know where device A is?, what does it broadcast?
Does it broadcast like chromecasts do via mdns?
Or does the stream cut off?
The issue mainly is that wireless isn't full duplex but half meaning that only one side can talk at the same time, so you can try converting multicast into unicast.
When you go to advanced settings -> luci (same password as gl ui) -> network -> wireless -> edit your wifi -> scroll down under one of these tabs.
Note that using this option can give issues, or rather wifi problems in some areas.
If that also doesn't work you can check if udpxy works in your situation.
Best is to go cable 
Thanks for your Response!
Let me specify: deviceA is LAN, deviceB ist LAN, only wifi connection is between AP and router.
my Setup was working when deviceA is also connected to the Router (with WiFi in that Case). Now, deviceA is Not Receiving Any Multicast data (other Services Like http or Ping are working of executed from deviceB)
deviceB is broadcasting to 239.0.0.1 on udp Port 1350. That ist almost all i know about that application. But it is Open source: trx: Realtime audio over IP
Hmm that is weird.
So you say it worked before on wifi for device A, and device B was on lan, right?
And now it doesn't work if device A is in lan, this is pretty weird because usually i would expect issues on wifi.
So that makes me wonder is there a involvement of a switch with maybe its own igmp stack?
239 multicast addresses are usually igmp.
Now im also wary with these things, but can you try to restart that switch first in case there is one?
if that doesn't change behaviour maybe we need to have a look into the switch settings, though i have to admit on my own switches i run my own igmp enabled stacks with openwrts they don't seem to conflict, but im also aware there is a small possibility of a stack conflict.
Yes, deviceA was in Routers WiFi.
A restart didnt Change anything
and there is a switch involved or not?
also can you check how this looks under luci?
go to advanced settings (login with password from ui) -> network -> interaces -> devices(tab) -> edit br-lan can you show me the advanced device settings tab?
if igmp isn't checked there it might be this issue, it could also be a mtu issue but only if it was extremely low (1500 is just fine), but something like 780 not, the higher size are even better also increase speed but only aslong that is allowed by isp,1500 is often safe (if you use things like a vpn connection you need to substract it's packet size from 1500 for the vpn interface, its not allowed to go above it what is defined for wan).
minimally you need 1280 mtu for ipv6 and for ipv4 it is a bit lower but i forgot the exact value just keep it on 1280 minimally.
when there is fragmentation you could see that with tcpdump especially with tcpdump -i br-lan -v multicast you will notice fragmented messages and also notice packets with 0 lengths, then you need to increase mtu 