Since a Rust update in early February, a major networking issue exists. The issue is explained on a technical level in this thread. Basically, the server.ip command isn't obeyed by Valve's Master Server. Therefore, it is more than likely reporting the incorrect public IP to the Valve Master Server.
In our situation, due to how our firewall is setup, we need the Valve Master Server to grab a specific internal IP (which will be sourced out as the Rust's external IP through a Source NAT rule). Unfortunately, it is grabbing the machine's internal IP instead of the IP we assigned it to using the server.ip command. The machine's internal IP is sourcing out as a different external address than the Rust's external address. Therefore, clients are requesting the wrong IP in the server browser and the server doesn't show up.
I will be emailing the Rust/Steam developers regarding this issue. According to the Rust developers, this is a Steam issue and they are investigating it. Though, it has been over two months now and no results...
Knowing Steam/Valve, we will more than likely have to investigate this issue ourselves and find out the cause directly.
Note - Our Rust server is currently not functional in the server browser due to this issue. Another task will be addressing a work-around I plan on implementing.
This is a project moved from our old Technical Tasks database to the Projects database. Some sensitive information may have been cut out when moving to the public.