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I have a Windows Server 2008 R2 DNS server (that replicated to two other servers) with a zone called mycompany.com. I created a new subdomain for that zone called subdomain.mycompany.com, this subdomain contained a single SRV record and a single A record.

I then decided that I no longer needed this subdomain, so I deleted it. After deleting the subdomain I needed to create an A record within the original zone with the same name as the old deleted subdomain. (subdomain.mycompany.com). However instead of creating the A record within the original zone, the record is created inside of a new subdomain with the name of the original subdomain.

This works, however it is not the intended result. Any ideas why the new A record is causing the deleted subdomain to reappear?

EDIT: This behavior is repeatable, but ONLY if the deleted subdomain contains an SRV record. I have replicated the problem on Server 2012 R2 as well. It's almost as if the DNS Server thinks that the subdomain still exists, so it brings it back from the dead and places the new host record inside it, rather than just placing the host record in the parent zone.

blacklight
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  • Please clarify. It sounds as if you deleted subdomain.mycompany.com from Zone A and then re-created subdomain.mycompany.com in Zone A and are wondering why it is suddenly back from the dead. Are you actually trying to say that instead, it created an entire new ZONE for subdomain.mycompany.com when you tried to create that record? That would make more sense. I am just having trouble understanding the exact problem from the information you have specified. – rubynorails Oct 12 '15 at 04:20
  • @rubynorails Thanks for the response. I deleted subdomain.mycompany.com from Zone A, and then created a new host record (A record) in Zone A called "subdomain". Instead of creating said host record (A record) in Zone A, it brings back the deleted subdomain called "subdomain.mycompany.com". To be clear, I am not recreating the subdomain, just trying to create a new host record in Zone A called subdomain. – blacklight Oct 12 '15 at 05:29
  • DNS can be tricky sometimes, so I assume it is either my recollection of how it works or yours that seems to be failing one of us at the moment -- but if you have a DNS Zone for `mycompany.com`, and in that zone, you create an A record for `subdomain` pointing to `192.168.1.123`, then you have in effect created a DNS record for `subdomain.mycompany.com`, which resolves to the IP address `192.168.1.123`. I feel like I'm still missing something here. – rubynorails Oct 12 '15 at 06:14
  • Ok perhaps I'm not being clear, I don't have access to the problematic server(s) right now, however I used my lab to take screenshots showing what happens. See this imgur link: https://i.imgur.com/SCmDplT.png – blacklight Oct 12 '15 at 08:07

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The thing to remember is that when you create a zone, you are not creating an entry in an existing database.

In fact, you are creating a new database as said in the documentation: A zone starts as a storage database for a single Domain Name System (DNS) domain name.

When you create a new entry, the DNS server checks if a relevant storage database exists. In your case a relevant, all be-it empty and inactive database existed.
The DNS server then reactivates the database, and puts your new entry in there.

Why it does this, I guess you'd have to ask Microsoft.

Reaces
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  • Great, thank you. This is the explanation I was looking for. Much appreciated. – blacklight Oct 12 '15 at 09:54
  • @blacklight Np, I'll see if I can find some more information as to why it behaves this way later. (And if specific timed jobs perhaps clean up the databases and stop the behavior from occurring) – Reaces Oct 12 '15 at 09:56