Telekom Media Receiver<->Gigabit Desktop Switch<->OpenWrt based router/ap<->Telekom Speedport

Dear community,

currently i am faced with a situation that needs to extend a network (range) with a wireless configuration. Unfortunately there is no chance to connect the Speedport right to the Media Receiver with a LAN cable (second floor). Luckily a OpenWrt based router (GL-AR 300M) is involved and could possibly made the configuration work. In short:

  • Telekom Speedport 724V Type C (DHCP server used over WIFI)
  • GL-AR 300M (WIFI based DHCP client to the Speedport, DHCP server [different subnet] to the TL-SG105S LAN cable attached devices)
  • Gigabit Desktop Switch [TL-SG105S] (wired to the physical LAN interface of the GL-AR 300M)
  • Telekom Media Receiver 401 Typ B lan cable attached (DHCP client to the to the GL-AR 300M) to the Gigabit Desktop Switch [TL-SG105S]
  • Some other devices as DHCP clients like stationary PCs/Laptops working as expected. No issues here.
  • All device operate IPv4 only (IPv6 disabled on all)

If you turn on the Media Receiver, everything works fine at first. Stream runs fine, no problems. But after 10-12 seconds, the stream starts to stutter and freezes at some point. AFAIK, the Media Receiver uses some sort of IPTV based Multicast to Unicast, tagged VLAN, IGMP etc. and thats where the devices fail (including me to make that work). I found several tutorials here (igmp proxy etc.) and on the internet but i couldnt make that thing work. Thats very frustrating at some point. So my question here is pretty obvious: How do i make it work? Pretty sure that i do have to forward something on the interfaces, possibly install other supporting packages...but what?

WWAN (red) on GL-AR 300M is the DHCP client over WIFI to the Speedport.
LAN (green) is DHCP server to the Media Receiver and all other clients over the wired Gigabit Desktop Switch.

For now i did reset the GL-AR 300M after failing using igmpproxy and other attempts. Now the device is (excluding the manually given adress range on the LAN interface/single static IP for DHCP server purposes) in pretty default configuration state (working in router mode).

Any help would be really appreciated.