SBS2003 DNS problems - client pc internet is intermittently slow

Posted on 2006-06-26
Last Modified: 2008-02-01
I have an SBS2003 server with 10 client pcs.

Just recently I have added a 4 new forward lookup zones in the DNS configuration. This seems to have caused the client pcs internet connection to slow quite dramatically; either internet requests timeout or the pages (such as yahoo or google) take up to 30 seconds to load. However there are times when the internet is running well which I presume is due to caching either on the server or the clients.

The server has the following services running: iis, dns, exchange & sql but does not have IAS. I plugged the internet connection directly into a laptop and it works very well.

Does anybody have any suggestions for solving this problem?
I have searched the internet without much luck. Is there a way to boost the DNS priority on the server to improve it's response time?
Question by:andychilds
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Author Comment

ID: 16982384
I have been troubleshooting the problem this morning and on the first try to sites (such as, an nslookup will time out 2-3 times before finally finding the correct ip address.
LVL 83

Expert Comment

ID: 16982418
Have you configured your machines to use an outside DNS server in the TCP/IP settings? If so, change that to use *only* your SBS as DNS server, and configure forwarders to point to your ISP's DNS server.

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Author Comment

ID: 16982428
The client PCs are configured to look at the server and I have configured two dns forwarders.
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Accepted Solution

Chris Dent earned 250 total points
ID: 16982444

The first thing I would suspect is the Forwarders. Remove those and see if you still get slow resolution.

Without them your server will use the Root Hints file (the servers listed under the Root Hints tab in the Properties for your DNS server), then it works down from those servers to get to the right domain - and you really shouldn't notice a speed issue with that.

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Author Comment

ID: 16982490
Thanks Chris-Dent, that has improved the performance.

But why has this made a difference though? I have been using dns forwarder ip addresses for over a year; why would it suddenly change?
I can only think that it is caused by the forward lookup zones I have added for the domain names that I host on the server. I have been adding them as primary zones, and then adding 'a name' records for www; is this the correct?
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Expert Comment

by:Chris Dent
ID: 16982563

> But why has this made a difference though? I have been using dns forwarder ip addresses for over a year;
> why would it suddenly change?

I couldn't say really... you're effectively handing off all the work to an upstream DNS, in this case your ISPs DNS. You would have to ask them to try and fix the problem - if they even admit there is one or can find it.

It could be something as simple as the server they use is getting old and generally getting unresponsive. Or they've got a lot more traffic being handled by it now.

Anyway, the change you've made means that instead of relying on your ISPs DNS to do all the running around your own server will do it. I normally prefer that configuration anyway simply because you don't have to put up with whatever happens at your ISP.

> I can only think that it is caused by the forward lookup zones I have added for the domain names that I
> host on the server. I have been adding them as primary zones, and then adding 'a name' records
> for www; is this the correct?

It should have no effect on name resolution except within the domains you have explicity added - and that's entirely intentional. There's certainly no reason for it to effect it in a more general sense.


Author Comment

ID: 16982572
Thanks very much Chris for all your help.
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Expert Comment

by:Chris Dent
ID: 16982581

It's a pleasure.


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