Unable to recognise some servers

I typed in the IP for a new prison server that I was going to try out but Minecraft couldn't recognise the server the IP address, the server in question's IP began with a 'prison.'. To begin with, I thought it was a problem with the server so therefore reported it to the server owner, but then I tried another server that started with a 'prison.' and that didn't work either, so I was beginning to think it was a problem with my client so I did a PC clean-up and reinstalled Minecraft completely and had no good results.

I am not sure whether or not the bug is reproducible by all Minecraft clients/users but thought this was a bug so reported it.
-Bozlid