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I am supporting a mix of Windows XP Pro and Windows 7 desktops in my Active Directory network, and I am having an odd issue with XP and CNAME records.

Say I have a record in my DNS for a server with an A name of something like and give it a CNAME of I can go onto an XP and 7 computer, and ping NAS and it will automatically resolve to If I am on Windows 7 and go to run and enter \\STORAGE or \\NAS, it will go to that server in Explorer. If I do the same in XP, STORAGE will work but NAS will not. It just times out

Is there some setting buried in XP to make this work properly?

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What is the error message that you get on Windows XP? – mrdenny Jan 12 '11 at 22:30

You're looking at two different kinds of name resolution. When you issue a ping command to a host name, you utilize the standard TCP lookup sequence (own host name, hosts file, dns server). This is true for both XP and Vista/7. This is why both the A and CNAME work

When you preceed a name with a double slash "\\", you are now telling Windows that you want to talk to a NetBIOS device, using NetBIOS name resolution. On XP, NetBIOS name resolution sequence (netbios cache, lmhosts file, WINS server, broadcast). In your example NAS is a CNAME in DNS, and is not a NetBIOS name. Note in the resolution order, NetBIOS does not use DNS for a name lookup.

If you want your XP machines to resolve "NAS" as a NetBIOS name, you will need to add it to your WINS server or to each machines local lmhosts file.

Look at to get started.

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+1 or you can also use the FQDN, ie \\ – Chris S Jan 12 '11 at 23:24

I'm not sure I agree with the NetBIOS answer. I've had to add the DisableStrictNameChecking value to the registry to get CNAME file shares to work. The following Support article references Windows 2000 and 2003, but in my experience is applicable to XP and Server 2008, too:

Edit: This would be needed on the file server, so no need to make the change on your XP machine.

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