Weird DNS timeout issue SBS2003

ubersonic · 9 Oct 2012 at 15:14

Hello, I have recently been having an issue with DHCP clients on our internal network, when trying to access a website it takes ~10 seconds to load. The problem was identified as a DNS issue with the server and sort of fixed by altering the DHCP scope to give the clients the networks router as their DNS server and this made sites load properly but obviously internal sites are now not working.

Internet access and site loading from the server itself is functioning fine its just the DHCP clients on the internal network that are having issues getting DNS resolved via the server. If I do an Nslookup from a client I can get an instant response from either the router or Googles 8.8.8.8 DNS server, however when trying our SBS box it times out on the first attempt then if re-requested responds instantly.

Any ideas? (before somebody suggests it, turning it off and on again has been tried).

knowlesy · 9 Oct 2012 at 15:23

have you restarted the router ?

try setting a pc to having a static dns and try that ? whats your net connection like speedtest.net / sync rate ? can you ping out if so what return rate and do you know what its been like before ?

have you tried opendns ? as well i have had problems with google in the past (once) have you got a firewall in between you and the router ? configured or changed any rules ? as well as that if everything is being so slow may be a ddos attack ?

it sounds like its from your server > router onwards ......

ethos · 9 Oct 2012 at 15:40

Are you using root hints and/or forwarders on the SBS 2003 box?

Please paste an ipconfig /all from the SBS 2003 server.

Little_Crow · 9 Oct 2012 at 16:04

ethos said:
Are you using root hints and/or forwarders on the SBS 2003 box?

Almost definitely this.
Most likely explanation is your SBS box has a duff DNS entry listed first in the forwarders, It has to wait till that times out, then it will try to the next one.

We had the exact same thing recently - the first forwarder listed was no longer responding. Spoke to our ISP and found the next 2 were correct, so just removed the non-responsive one.

ubersonic · 9 Oct 2012 at 16:40

Little_Crow said:
Almost definitely this.
Most likely explanation is your SBS box has a duff DNS entry listed first in the forwarders, It has to wait till that times out, then it will try to the next one.

We had the exact same thing recently - the first forwarder listed was no longer responding. Spoke to our ISP and found the next 2 were correct, so just removed the non-responsive one.

Jackpot, One of the company DNS servers was decommissioned last week and it was still in the forwarder list at the top, talk about n00bish mistake /facepalm.

Thanks guys