@Gargron huh ... interesting. I have mastodon containers and a peertube container running on the same host in a docker network. They can't talk to each other over public IPs because of NATing. Docker supports --add-host (or ExtraHosts in the API) to add /etc/host entries at launch, which I pointed to the internal IP of the load balancer.

I guess I should just get source nating to the public IP working.