Ran into a situation with a remote CM12 console being unable to connect to a site server. According to the local SMSAdminUI.log file:
Transport error; failed to connect, message: 'The RPC server is unavailable. (Exception from HRESULT: 0x800706BA) '\r\n Microsoft.ConfigurationManagement.ManagementProvider.SmsConnectionException \r\n The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)\r\n at Microsoft.ConfigurationManagement.ManagementProvider.WqlQueryEngine.WqlQueryProcessor.ExecuteQuery (String query, Int32 blockSize, Dictionary`2 contextInformation)
Initial troubleshooting indicated that this was a problem with the Windows Firewall blocking remote administration. However, the firewall was off one the site server. Yet some posts indicated that the ports needed to be allowed, regardless of the firewall being on/off. So I opened up those, but it still couldn’t connect.
I took a step back and went to the basics – could I ping the FQDN? No, I couldn’t! Yahtzee! I could ping the short name just fine, so I just needed to have Windows map the IP to the FQDN. So as a quick fix, I just added an entry into the C:\Windows\System32\drivers\etc\Hosts file – and voila, the remote CM12 console could now connect!