We had a single reverse lookup zone in our 2008 DNS with the name:

220.10.in-addr.arpa (I'll call this the mother zone) which was hosting records from 3 different subzones / child zones:

10.220.0.x, 10.220.1.x and 10.220.2.x.

In trying to separate records of one zone from the others, I created initially two zones, 0.220.10.in-addr.arpa and 1.220.10.in-addr.arpa that are replicating to all DNS servers in the domain. At first, these zones appeared at the same level as the 220.10.in-addr.arpa but then after a while two grayed out containers corresponding to each child zone showed up underneath the mother zone in addition to the individual ones I created.


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Why are these containers grayed out and why did they not show up at the beginning? Does grayed out mean that they are delegated?

Thank you.

up vote 3 down vote accepted

When you create an rDNS zone for the parent network 10.220 the DNS service will automatically create a child zone under the parent zone for each subnet of the parent zone (network) that it discovers when clients from those subnets register their PTR records. You've wound up with delegated zones under the parent zone because the DNS service has discovered that you've already created zones for those subnets so it creates a delegated zone under the parent zone that points to your manually created zones.

The way I prefer to do it is to create a rDNS zone for the parent network and let the DNS service create the child zones when clients from those subnets register their PTR records. This is the opposite of what you've done so let me clarify:

If you want to manually create zones for each subnet then don't create a zone for the parent network (10.220).

If you want the DNS server to create the child zones for the subnets that fall under the 10.220 network/DNS zone then delete the 10.220.0 and 10.220.1 zones that you manually created.

  • Thanks Joe. That's what I was looking for.Now, I understand that functionally it doesn't make much of a difference. But in cases where you might have thousands of records to look at, a separation of the different zones could split the task up a bit. I could live with all of them under the same zone though. I was just not certain how the process worked. I removed the x.x.0.x and x.x.1.x though and restarted one of the clients in the x.x.0.x. The PTR record and the sub-zone were not created automatically under the reverse zone. The clients are set up with DHCP reservations. Any idea? – Bourne Aug 5 '11 at 4:46
  • Update: the client's PTR record did show up under the 220.10.in-addr.arpa but I still don't see a sub-container inside of it labelled 0. – Bourne Aug 5 '11 at 6:04
  • @Bourne: The behvior I've seen is what I've described in my answer. I'm not sure why you're not seeing it now though. I'm wondering if it only occurs with traditional "classful" networks and not "classless" networks. Try creating a parent rDNS zone for 10.0.0.0 and see if the DNS server creates the child zones for the subnets. Make sure to delete all of the existing rDNS zones first, which won't do any harm as rDNS zones aren't required for the proper operation of DNS or AD. – joeqwerty Aug 5 '11 at 12:13
  • Thanks Joe. I tried that but it didn't work. I guess I'll try to do some more reading. – Bourne Aug 8 '11 at 3:40

Yeah, those should be delegations - if you click on them, the only records present are of type NS, correct?

They were likely auto-magically generated by the DNS server, as it knew it had something screwed up hierarchically.

  • Yes, they only contain NS records. Do you have any suggestions as to what the correct way to set them up is then and not have them be grayed out? This is just a single domain environment so I don't know why it would bring delegation in the picture. I can't seem to find a way to "directly" create a child zone underneath the parent. – Bourne Aug 5 '11 at 3:03
  • @Bourne DNS delegation isn't related to active directory at all; all it's doing is marking those sub-domains (which 0 and 1 are) as existing in a different zone - it happened to know about them, and where to point them. If you're a DNS server, and you're hosting a DNS zone for 0.220.10.in-addr.arpa, and a zone for 220.10.in-addr.arpa, how do you know which zone to look in for what you're going to serve? That's all it's doing: maintaining logical consistency in the DNS structure. As to how I'd suggest doing it: keep it all in the same zone; what are you trying to separate? – Shane Madden Aug 5 '11 at 3:15
  • Thank you. Your comment makes sense. The 3 zones that I'm working with are all part of the same big "subnet" so clients in each of them can talk to one another. The reason I'm trying to separate them is because each subnet has been designated for a different purpose e.g. administrative, client machines and dhcp pool and this would hopefully ease maintenance on various records. Also, you could achieve this in 2003 pretty easily. Don't know why you can't in 2008 – Bourne Aug 5 '11 at 3:31
  • @Bourne: I don't see how your "administrative" separation is relevant to your DNS infrastructure or how it eases your maintenence. Not nitpicking, just trying to understand the logic. – joeqwerty Aug 5 '11 at 3:50
  • @Shane: Based on the rep you've earned in the time you've earned it, it looks like you're on the fast track to give Evan a run for the top spot. – joeqwerty Aug 5 '11 at 3:53

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