Database Mirroring Error 1418 Troubleshooter

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I've been posting in the MSDN and TECHNET mirroring forums in the last few days and I've noticed a lot of occurrences of the 1418 error which I have referred to briefly in this blog before. Therefore I thought I'd post a 1418 specific troubleshooter for reference. The problem we're trying to solve is that you try to start database mirroring and you receive this error:

Msg 1418, Level 16, State 1, Line 1
The server network address "TCP://myserver.domain.domain.domain.com:5022" can not be reached or does not exist. Check the network address name and reissue the command.

The following assumes that:

1. You are using separate physical servers for the mirror partners. If you're not, you might this to read this about configuring mirroring on local instances and a typical problem you can come across.

2. You're using domain accounts for SQL Server services

3. You're using windows authentication and you're not using certificates

4. You've already read this, or are familiar with the overall principal.

So here are the things that I would check:

1. Have you restored a fairly recent full backup to the planned mirror server, with NORECOVERY. Have you then restored a transaction log, also with NORECOVERY. If you haven't you won't be going anywhere with mirroring. Maybe you should read this first :-)

2. Have you configured your endpoints correctly. To be specific, this means:

a) Are they started

b) Are they using the same form of authentication

c) Are they using the same form of encryption

d) Does the service account have permission to use them

Even if you think or assume you have done this correctly (including if you've used the wizard to configure them) don't assume they are correct. You've encountered an error and you need to be sure. You need to script each endpoint and check that all the settings are correct. I've seen this happen too many times to mention, where people thought they were OK (because they "ought" to have been) but it was something simple like one of them wasn't started. Using the wizard does not guarantee that everything will always work. Remember all the wizard does is execute T-SQL, so mistakes or problems are still possible.

3. Are the ports you have selected valid, and are they open? Are they being used by any other processes? Can you telnet to the port?

4. Is there a firewall (hardware or software)? Have you created an exception / rule to the firewall? Windows firewall is no exception to this rule. It will block mirroring traffic just as much as any physical firewall will.

5. Is the FQDN valid? Can it be resolved? Again, can you telnet to it? If you're not using FQDN and you're using direct IP addresses, the same rules still apply. Can you telnet to it? If you're not using FQDN or IP, have you checked the above post for resolving names locally.

I hope this helps. It's my experience that these points will solve the majority of 1418 errors. If you have any questions about this topic feel free to post here or in the forums.

Graham