Xserve Services are accessible for a moment and then can't access

Question

I have new Intel Xserve. Set up as a gateway, open directory master, web server, etc. Ethernet 1 connects to the wan and Ethernet 2 connects to a new Airport Extreme. The client machines are Macbooks. The Xserve is set up to be the dhcp server. The Airport is a bridge.
Everything was working fine until last week. Here is what is happening: The Macbooks can use the services that the Xserve provides for a short while, ie they can browse the Xserve's websites, browse internet websites and authenticate with open directory. Then after a short while they can't. For instance attempting to get to www.apple.com with the Macbook will result in a constant "contacting ...." status in Safari. Authentication with Open Directory is no longer possible. Even trying to browse 192.168.2.1 (the Xservers Eth2 IP address) results in "contacting...." and nothing happening. Interestingly I can still ping 192.168.2.1 from the laptop.
To get things working again I've found I can simply make a change to the setting of the ethernet card on the Xserve. For example I might switch it from static ip to dhcp and back. I might change the ethernet from auto to manual and back or whatever. Just make a change to the network settings and apply then change them back and apply. The laptops will be able to access the services again for a short while (maybe a minute or two) and then things get stalled again. They won't be able connect to websites or get access to the internet etc. Again even http://192.168.2.1 won't work. Change something in network settings and change back and it will work for a short while again. Nothing is popping out at me in any logs I'm looking at.
Do I have a hardware problem? At first I assumed DNS perhaps? Since the server is pre-production I erased the harddrives last night and reinstalled OSX Server. Set it up as a gateway and webserver using the apple setup aids and the same thing. Laptops can access the server for a few moments then fail. If I make a change to the networking settings in preferences that seems to reset things for a short time and then it fails again.
I'm stumped, but then again I'm also new at this.
Xserve   Mac OS X (10.4.9)  

Answer 1

&tWhen the clients keep on showing the "connecting..." screen, that is usually a DNS problem. Do you have the DNS servers correctly listed under DHCP services by the server?
If you can ping your server but cannot access the Internet try the dig command and see if the DNS servers are responding.
;b>dig www.apple.com
The last few lines should contain the IP address of your DNS server like this:
e.g. Covad DNS server
;; Query time: 25 msec
;; SERVER: 64.105.189.26#53(64.105.189.26)
;; MSG SIZE rcvd: 284
If the IP address shown there is not the one for the DNS server, you have configuration problem.