DNS problem

[mrb-solutions]

Hello,

 

We are having a little bit of trouble with our DNS server at the moment where for some reason all of our clients are loosing access to the internet and exchange server. When you click on the network adapter and troubleshoot it comes up with the error message "DNS server not responding" however we have found a way around this for now which is in command prompt to flush dns and ipconfig /renew but this is then happening again every 20 mins or so. I am getting worn our running around the school sorting this out for everyone.

 

Any help would be great.

[jinnantonnixx]

Anything in the DNS section of event viewer on the DNS server?

[mrb-solutions]

Nothing i can see. I have currently set my network adapter to manual DNS entries of the two servers and seems to be stable at the moment however mine was always a funny one, sometimes being ok for most of the day.

 

We have had CSE in looking into it but im not really a fan at all of someone looking after our network as its just one big bodge job.

[paulellam]

what OS etc? Anything in Netdiag and dcdiag?

[mrb-solutions]

Sorry,

 

Windows 7 32 and 64 bit. Server 2008R2

 

Not sure how to get to them, pointers necessary

[Netman]

Have you run dcdiag yet? If not, then try that...

 

Linky http://technet.microsoft.com/en-us/library/cc731968(v=ws.10).aspx

Edited May 16, 2012 by Netman

[jinnantonnixx]

Try NSLOOKUP in debug mode,

 

NSLOOKUP

>set debug

>name-of-your-server (or other suitable site to check)

 

 

If you have DNS suffixes appending, you'll get a few rcode=NXDOMAIN in your answers, but you should get the correct answer if all is well. It's a useful tool for tracking down where DNS is going wrong.

Edited May 16, 2012 by jinnantonnixx

[jinnantonnixx]

Just spotted you have two DNS servers.

 

Under the 'Properties' of your forward lookup zone (do this from each server in your DNS view), do the correct name servers show up? Are your dynamic updates set to 'secure only?'

Edited May 16, 2012 by jinnantonnixx

[mrb-solutions]

no errors but i see that our refresh rate is every 15 mins which would explain after flush and renew that 15 mins later it is not working again. A PC in the office was not working and we added the DNS manually to the adapter and refreshed internet and it worked. I think there must be a problem with the clients being able to see the DNS server as once it points to it, it seems to work fine..

[jinnantonnixx]

Are you setting the DNS address on the clients via DHCP? This is the best way.

 

Also, have you got competing name-resolution services running, like WINS service?

[mrb-solutions]

Dynamic updates are set to Nonsecure and Secure... hmm but the other DNS server does show up in Forwarding.

[jinnantonnixx]

Are the zones set up as AD Integrated? If so, and it's a copy (replicated), it shouldn't be in forwarding - that just doesn't make sense. Perhaps this is the fault. Edited May 16, 2012 by jinnantonnixx

[psydii]

Recomended best practice for Windows Domain integrated DNS

DomainController_A:

In the network adpater ->TCP/IP settings->DNS Servers

Entry1: 127.0.0.1

Entry2: IP of DomainController_B

Ensure that there are no other DNS servers configured in the 'Advanced' settings.

 

In the DNS Server Management tool

Select DomainController_A click thorugh to Properties->Forwarders

Make sure that only your ISP's DNS servers are there.

Check the Scavenging interval and related settings Understanding Aging and Scavenging

 

DomainController_B:

In the network adpater ->TCP/IP settings->DNS Servers

Entry1: 127.0.0.1

Entry2: IP of DomainController_A

Ensure that there are no other DNS servers configured in the 'Advanced' settings.

 

In the DNS Server Management tool

Select DomainController_A click thorugh to Properties->Forwarders

Make sure that only your ISP's DNS servers are there.

 

 

 

Are any of your servers getting their addresses from DHCP? Are any of them multihomed?

 

 

On your DHCP server(s) ensure that they are configured to only give out the DNS addresses of DomainController_A and DomainController_B

 

 

On your clients ensure that they are either getting their DNS settings from DHCP or they are cofigured to use DomainController_A and DomainController_B only.

 

Also check that when your client loosed connectivity - is it able to ping your DC's and your gateway without packet loss?

Edited May 16, 2012 by psydii

[mrb-solutions]

Just a quick one to say that all is resolved now with help from CSE. Seems DHCP was referencing old DNS servers - how annoying