Frequent DNS problems

[Fat Tone]

In my office I have a Dell Windows Server 2008 64 R2 box acting as DC and Exchange. It runs DNS. The connection to the outside world is through a Draytek 2820 router.

When in the office, we all find that very frequently the first request for a web page will immediately fail (page cannot be found) but a refresh will generally work (some people report that often more than one refresh is required).

I'm guessing that this is a DNS lookup failure but don't know how to go about proving and fixing it. DNS has sometimes (but not for quite a while) fallen over completely which restarting the service fixes, but that and/or restarting the router doesn't help now.
There are a couple of switches dotted about too if that matters.

Suggestions very welcome.

Many thanks,

Tony.

[UtwigMU]

Check DNS forwarders on the server, they should be your ISP DNS servers, then maybe openDNS, google,...

Who is DHCP server: server or router?

Have DHCP server give your server as first and one of your ISP's DNS servers as 2nd DNS.

Also what is internal domain, is it same as your external domain?

mydomain.local or is it mydomain.co.uk?

[Jammrock]

I think Utwig is right, it's probably your forwarders.

- Open DNS
- Right-click the server name and select properties
- Forwarders tab
- You can try your ISPs DNS but chances are there are faster options. Personally I would use Google's Public DNS (8.8.8.8 and 8.8.4.4). OpenDNS will resolve an IP even when it shouldn't. Say you "ping aslkjdfoiwefa.putz", Google correctly returns "Ping request not found..." OpenDNS returns one of their 208.xxx.xxx.xxx IP addresses which can mess up automation and confuse techs who don't know much about OpenDNS, or that you're using it.


Make sure you check your server resources. Since you are running so much on the server there is a chance something is slowing down DNS resolution due to resource restraints. With Exchange on there it could be anything, but I would look specifically at disk IO and RAM.

[Fat Tone]

Cheers Guys.

Sorry for the delay in responding, have been out of the office.

The server is doing DHCP. internal domain is mydomain.local.

Looking at the Forwarders tab it contains the IP of the router (192.168.93.1) with as Server FQDN of my.router.

Server CPU load is generally low, the HDDs are super-fast, but the 4GB RAM could perhaps not be enough?It is showing 580MB cached, 9-10MB free

Looking at the router configuration it lists two DNS server adddresses both provided by my ISP.

[UtwigMU]

Have server use your ISP servers as forwarders. See what DHCP is handing out as DNS servers to workstations.

[Fat Tone]

Finally got a chance to look at this yesterday. I changed the DNS settings in the router to 8.8.8.8 and 8.8.4.4 and everything has been going swimmingly so far. I have reported the DNS problem to my ISP and we'll see what he says.

I did try entering other IPs in the Forwarders section but it wouldn't take. I also said something about needing reverse lookingups configuring and I don't know enough about that at the moment so I left alone.

Thanks for the advice

[VJ]

I recently have been suffering problems to some Belgian computers... I also suspect it to be a DNS issue, but it is annoying as one of them is my mail server...