Can't claim server from different subnet

I just installed Plex Media Sever today and had to connect to (hostname):32400/web from a system on the same subnet in order for it to let me register it.
The server is using the latest non-beta build for Linux but I was able to reproduce this behavior on my Windows PMS server as well.

I was able to access the server directly via web browser, and logging in did give me the plex shell but the option to claim/register it was not presented until I went to the server from a system on the same IP subnet.

Server’s IP is 192.168.4.21
Desktop IP is 192.168.3.40
I verified that the following ports were allowed through the firewall router
1900,3005,5353,8324,32400,32410,32412,32413,31414,32469

Is this a safety built into the platform by design?

Yes, that is built in by design.

It’s intended to prevent your server, should it be on a remote network somewhere, from being claimed by someone else if it ever got into a logged-out state.

There are two solutions:

  1. SSH tunnel (e.g. ssh -L 8888:127.0.0.1:32400 ip.addr.of.host and then http://127.0.0.1:8888/web to claim )

  2. SSH and curl using a Plex Claim token.