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Given a Windows domain, with DNS provided by a server on that domain, I am curious about what happens if a guest joins the network attempting to use the same hostname as an existing server, and then tries to register that hostname in DNS with its DHCP address. Can this potentially be disruptive to the server, or is Windows DNS smart enough to spot a duplicate hostname and deny an auto-register request from that host? What actions can be taken to ensure that DNS for a hostname cannot be altered?

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Microsoft's solution to the "fileserver.domain.com" scenario you outline in a comment to TomTom is "Secure dynamic updates".

Your DNS zone must be Active Directory-integrated in order to use the feature. Records registered in such a zone are protected by ACLs and the updater must successfully authenticate as a user / computer with rights to modify an existing registration.

There are ramifications for DHCP servers in such an environment. The DHCP server, if it is to register records on behalf of clients, must have a credential that permits it to do so. This article talks about the considerations for DHCP and DNS dynamic updates and describes what I'm glossing-over here in detail.

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Thanks, that gives me a nice launching point for understanding it. –  Aszurom May 19 '10 at 16:39
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Duplicate hostnames are explicitely allowed, so the server can not really stop that.

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So if I know there's a server named "fileserver.domain.com" and I change my PC's hostname to "fileserver" and get DHCP from a domain.com DHCP server... what happens to DNS for fileserver.domain.com? Can I then snatch traffic away from that server? –  Aszurom May 10 '10 at 17:53
    
No idea - in companies normally not a problem as... well.... computer names within the domain are controlled. People can not rename their computers ;) Otherwise - really no idea. I think DHCP will not register the name - it likes to set the only name. But this isaa windows DHCP thing, not a DNS issue. DNS allows multiple IP's for one name. –  TomTom May 10 '10 at 18:08
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