Windows printing with a CName

Once you have the cname in the DNS server enter the following registry keys.

HKLM\system\currentcontrolset\services\lanmanserver\parameters
Add value
Value Name: OptionalNames
Data type: REG_SZ
Value Data: "alias.alias.com"

HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value name: DisableStrictNameChecking
Data type: REG_DWORD
Radix: Decimal
Value: 1

Then run the following commands

setspn -a host/aliasname targetserver

setspn -a host/aliasname.alias.com targetserver

Reboot the server.

Taken from the following technet article.
http://support.microsoft.com/kb/281308