DNS reverse zone active directory

mrbayIt
mrbayIt used Ask the Experts™
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hi, i have a question about reverse zones for my active directory environment.

Lets say site A, is a super netted site. 172.20.0.0/19
within that supernet, are smaller networks

subnet A   172.20.0.0/23
subnet B   172.20.2.0/23
Subnet C   172.20.4.0/23
Subnet D   172.20.6.0/23
Subnet E    172.20.8.0/22
Subnet F     172.20.12.0/22
Subnet G    172.20.16.0/20

For reverse zones, is there a way to define the entire subnet either by the /19, or example subnet A with the /23 or do i have to define each one the way it is presented in the wizard, as in since 32 total subnets in that /19
i would have to define each /24 subnet?
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PowerShell Developer
Top Expert 2010
Commented:
Only by creating the zone as /16, but there are no other choices, reverse lookup zones follow classful addressing boundaries (/0,  /8, /16, /24 and /32 only).

This isn't an MS limitation (or a limitation of the wizard), it's a limitation in the DNS service.

Chris
Svet PaperovIT Manager

Commented:
Yes, classless reverse lookup zone can be created but there is actually one situation when it will make sense – when you are delegated with managing a subnet of a classful network. Otherwise, just stick with the classful ARPA standard. The following example is for Windows Server 2000 but it will work in 2008 too. http://technet.microsoft.com/en-us/library/cc961414.aspx
Chris DentPowerShell Developer
Top Expert 2010

Commented:
Classless zones are entirely reliant on delegation from a classful zone. It needs a CNAME to rewrite from one zone to another. You'd still need to create the /16, and your overhead would be significantly greater.

Chris
DrDave242Principal Support Engineer

Commented:
Be aware that classless reverse lookup zones cannot be dynamically updated. This is mentioned in the article linked above, but it's easy to miss:

No Dynamic Updates on a Classless Reverse Lookup Zone

I strongly suspect this also applies to Server 2012 and 2012 R2.
Chris DentPowerShell Developer
Top Expert 2010

Commented:
(for confirmation) It will, the nature of classless zones prohibits (RFC compliant) dynamic update methods.

Chris

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