Hi trendy and amteza,
thanks for the reply. WDS wont be supported by the ISP router (a german Telekom based Speedport 724V) and sadly no Mesh support neither. The relayed option works just fine. The attached LAN devices on the WL-755 will get a IP from the base router. Regular traffic works as expected. The next issue i am faced with is the so called "Media Receiver" (Telekom based Media Receiver 401). Thought the relayed option would work out of the box with the IP TV stuff But it doesnt. Booting and connecting the Media Receiver using the WL-755 over relayed works with no unexpected behaviour. After successfully booting, every channel opens just fine at first but starts to stutter after ~10 seconds and finally the video stops. Afaik this is related to a mixup with IGMP, UDP, Unicast to Mullticast. This is the same issue others faced as described here:
https://forum.openwrt.org/t/solved-iptv-igmpproxy-and-firewall-issues/12890
I found a general tutorial on this IPTV topic with UDP/Unicast/Multicast with OpenWrt:
https://openwrt.org/docs/guide-user/network/wan/udp_multicast
Currently i wasnt able to make it run successfully.
thank you for your reply
K.