How to accept DNS alias on Windows Servers

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In some cases, you will need to set two different names to a Microsoft Windows Server. A good example is a file server or print server migration, when you want to have a new server with a new hostname, and redirect all the traffic from the old server name to the new server.

As you probably know, the best solution is probably to set a DNS alias, but Microsoft Windows 2003 and Windows 2008 servers will not accept connections with a different hostname as destination. This is a security feature that needs to be disabled, by modifying the registry and running a command line on the new server.

There is the procedure to add a SMB alias on Windows 2003 and WIndows 2008 R2 servers:

Add a CNAME record in your DNS pointing at the primary server name, e.g. fileserver.mydomain.local CNAME server1.mydomain.local
Open the Registry Editor (regedit) on the server and browse to: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
Add a new REG_DWORD 32bit entry using the edit menu
1. Value name: DisableStrictNameChecking
2. Data type : REG_DWORD
3. Radix : Decimal
4. Value : 1
Exit the registry editor then reboot your server
Once the server reboots you need to add a Service Principal Name (SPN):
1. Open the command prompt
2. Type: setspn -a host/fileserver server 1 (where 'server1' is the primary name of your server and 'fileserver' is the alternate name)
3. Type: setspn -a host/fileserver.mydomain.local server1 (where fileserver.mydomain.local is the fully qualified domain name alias and server1 is the primary name of your server)