During the past days I was working in a Database Mirroring Configuration and one of the errors I got was the following:
Msg 1418, Level 16, State 1, Line 1
The server network address "%.*ls" can not be reached or does not exist. Check the network address name and that the ports for the local and remote endpoints are operational.
It was presented when I run the command:
ALTER DATABASE TestMirror SET PARTNER = 'TCP://hostname:5050'
The server network endpoint did not respond because the specified server network address cannot be reached or does not exist.
To solution my problem, I accomplished the following points:
1. The ENDPOINTS should have the status started.
select state_desc from sys.database_mirroring_endpoints
2. The system should not be behind a firewall.
3. Make sure that the principal server instance and mirror instance are listening on the right ports and whether are available.
4. Name pipes protocol enabled.
5. The same username and password were used to run SQL Server services on both machines.
6. The usernames to run SQL Server services have NT Auth Access between both machines.
7. Make sure that the username for the SQL Server services has rights on the SQL Server instance.