cannot unc by ip address

I am trying to connect to another PC using the following unc… \\ipaddress\share name. However, I get The network path was not found”. I do have the proper credentials so that is not the issue. However, when I put the computer name/ip address in my hosts file I can access the share using this unc…\\computername\share name. The question is…why does the second way work and the ip address does not?