DNS issue

[adamsund]

This morning we had an issue where there were no IP addresses left in a particular DHCP scope. I explained to my tech that he needed to delete all the leases and this would free up the redundant addresses for some computers that were getting 169 addresses. Unfortunately, the tech went into DNS and deleted almost every entry in our domain (barring servers). Since then, our devices have lost connectivity to all our local resources. Thankfully, staff data is mostly on Office365 now so they can still access them. Unfortunately MIS access has gone along with other local storage.

 

I have a feeling that it's going to be more of a waiting game for this issue to fix itself, but I won't be able to rest all weekend in the hope that this will work on Monday morning! DHCP is assigning addresses with no problem, but the DNS entry isn't being created. If I add it in manually then it doesn't work either. If I nslookup any servers from clients, they come back fine. If I try and ping then the host cannot be found.

 

Please help!

[Fazza]

You may need to reboot the servers for them to automatically update the DNS records on the DNS server. Start with your DNS server and then reboot another one that wasnt working just to confirm this fixes it and then use something like RemoteRebootX to schedule reboots either tonight or over the weekend.

[adamsund]

Hi Fazza,

 

I've already rebooted both DC's which are also the DHCP servers to no avail. I've enabled the log in event viewer and the error message given when pinging is "DNS Name resolution for the name, [DC], failed because the client was unable to contact DNS servers. At least one of the interfaces is not in a private network and name resolution will not fall back to LLMNR or NetBIOS"

[FN-GM]

Set your DHCP Scope options like the attached and the machines should update DNS when the lease is renewed. If you reboot the machines it will force a renewal of the lease.

 

Advising someone to empty DHCP is also a bad idea. It will result in duplicate IP address and other DNS issues.

[Fazza]

Hi Fazza,

 

I've already rebooted both DC's which are also the DHCP servers to no avail. I've enabled the log in event viewer and the error message given when pinging is "DNS Name resolution for the name, [DC], failed because the client was unable to contact DNS servers. At least one of the interfaces is not in a private network and name resolution will not fall back to LLMNR or NetBIOS"

 

If the DC you rebooted isnt showing up in DNS then not sure what's going on then. Normally a reboot of an affected computer sorts it out as it re-registers with the DNS server.

[adamsund]

Set your DHCP Scope options like the attached and the machines should update DNS when the lease is renewed. If you reboot the machines it will force a renewal of the lease.

 

Advising someone to empty DHCP is also a bad idea. It will result in duplicate IP address and other DNS issues.

 

I admit, it was a bad idea.

 

The scope option were already set similarly to yours anyway (just the third tickbox down not ticked) but I matched them up. Unfortunately the issue remains! The DNS entry has created now though, but I still can't contact any network resources.

[Marcs_Dad]

If you can connect to the remote devices then the command ipconfig /registerdns will be your friend. Below is a one liner that I knocked up some time back to do just this. You will need to download psexec.exe which is part of the Sysinternals suite that Microsoft now own and provide free. Good luck :-)

 

echo off

rem Use - Forces a client to re-register DNS record

rem

rem Usage - RemoteRegisterDNS.bat TargetComputerName

 

 

c:\psinstalls\psexec.exe \\%1 ipconfig /registerdns

 

Save the listing above into a file called RemoteRegisterDNS.bat and then run it from an advanced command prompt with a computer name or IP address

Edited November 16, 2018 by Marcs_Dad
Amendment

[adamsund]

Thanks everyone for your help and suggestions. I've finally discovered and fixed the issue and thought I'd post here just in case it happens to anyone else. We use DirectAccess here and one of the deleted DNS entries was for the DirectAccess network location server (directaccess-NLS). This meant all mobile devices with DirectAccess enabled tried to connect to the NLS and couldn't so tried to connect to DirectAccess. When trying to connect to any resources it was using DirectAccess's dns servers which it couldn't connect to because the devices were on-site. My massive headache has now lifted!