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DHCP / DNS Missing A Record

mrsold
Techie
Posts: 8
14595     0

We have multiple hosts as of late that sucessfully pull a DHCP address and are domain machines that there is no A record being created for the host.  I can do a reverse lookup on the IP and that works but not name to IP.

 

Any thoughts?

Re: DHCP / DNS Missing A Record

Adviser
Posts: 200
14596     0
Did you enable option 81 in the DHCP settings on the DHCP server (in the Grid)? You may have to tell the DHCP server to ALWAYS update as it may be negotiating with the client. The client will always attempt to do the update itself but, with default settings, it will be unable to. Generally, it’s recommended to have the DHCP server perform the updates since it’ll clean up when the lease expires while the client won’t (generally it couldn’t since it wouldn’t be online).

Re: DHCP / DNS Missing A Record

mrsold
Techie
Posts: 8
14596     0

Option 81 is NOT enabled on the scope.  It looks like historically, we haven't turned that on.  It seems odd that we've been OK up to this point but now we have some hosts that we are missing info on.

Re: DHCP / DNS Missing A Record

Adviser
Posts: 200
14596     0
The DHCP server will only update the reverse zone by default. You have to configure it to update the forward zone so either you’ve had it configured that way previously or someone modified the settings to allow some (or all) systems to update forward zones (A records) based on where they are coming from or via GSS-TSIG updates. Double check your DHCP server settings for that network/range and make sure it’s got the information needed to allow the DHCP server to perform the forward registrations. I would start at one of the ranges just to see if the values are inheriting. If not, then move higher until you find where you want to set it and it’ll inherit down unless overridden.

Re: DHCP / DNS Missing A Record

TTiscareno Community Manager
Community Manager
Posts: 361
14596     0

If DDNS updates are enabled in the DHCP properties, the DHCP server will attempt to add the A and PTR records along with a TXT record by default. This is controlled based on the TXT record handling configuration which is set to "ISC" mode by default.

 

The TXT record includes a hash value generated based on the clients MAC address. In ISC mode, if an A record exists, the TXT record must also exist and match the expected value. If an A record exists but there is no TXT record or the value does not match, then the DHCP server will not update the A record.

 

The system logs would help explain why any updates may be failing and assuming that your logs have not rolled, you can filter by the clients hostname (NOT FQDN). The other thing to check for is that the Updates ACL's on the zones only allow the DHCP server (which is done by default for Infoblox DHCP servers in the Grid) and special/statically configured clients to do updates. If this is open to DHCP clients, they can step on the DHCP servers toes.

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