Unless you actually specified otherwise, docker containers do NOT run on the same subnet as the host. Instead they use the (horribly inaccurately named) bridge network which is in fact NAT routing with some port forwarding. If you require keeping with “bridge” networking, then you will need to do a fair amount of setup to make things work correctly (GitHub - plexinc/pms-docker: Plex Media Server Docker repo, for all your PMS docker needs.)
Alternatively you can use either host or macvlan networking and then your server will really be on the same subnet as your host and not have to any such steps.
OK I have tried the other subnets option - doesn’t work - makes no difference
I’ve created a macvlan and everything looks OK - but no connectivity to the plex instance either externally or directly on the host. The host in this instance is Windows 10 using WSL…
Please provide details on what you’ve tried and info from your server (i.e. logs) after these attempts so we can check what’s going on. If your server sees the connection coming from the correct IP subnet then it should be able to treat them as local. If this isn’t working, then it’s possible it’s not seeing the subnet, but instead the connection from the client is going out through the internet and then back into your server. In which case, this is some sort of network configuration issue. Using a manually specified server IP would not assist in this case.
