DAC is a very good feature in SQl server but can be frustrating if you are not able to connect DAC with SQL instance.
So its always advisable to test it before you are forced to do.
So here couple of errors i faced
1. Error: "A network-related or instance-specific error occured while establishing a connection to sql server was not found or was not accessible. Verify that the instance name is correct and that sql server is configured to allow remote connections.(provider: SQL Network Interfaces, error: 43 - An error occured while obtaining the dedicated administrator connection (DAC) port. Make sure that SQL Browser is running, or check the error log for the port number) (Microsoft sql server)"
Reason: As error says please check if sql browser is up and running fine (not hang)
2. Error: "A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: TCP Provider, error:0 - The specified network name is no longer available.)(Microsoft Sql server, Error: 64) The specified network name is not available"
Reason: DAC listener is not enabled , (Enable it)
3. Error "Could not connect because the maximum number of ‘1’ dedicated administrator connections already exists. Before a new connection can be made, the existing dedicated administrator connection must be dropped, either by logging off or ending the process."
Reason : Some one already using DAC (Check who is using)
4. You many need to get firewall ports opened as well, depending on your environment and where you intend to connect from. This will probably be port 1434, but that will vary depending on your configuration.
--> Check with your network Team