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I have a Win2k8 R2 server and Win 7 clients. The Server has DHCP and DNS running on it. So far so good everything works fine.

Now the problem comes when I also enable DHCP on the router so that clients can get an Internet connection when the Server is down. This is on the same subnet but a different IP range.

If the clients happen to pick up their IP from the server then all is fine but if they get it from the router's DHCP then the DNS record on the server does not get updated even though dynamic updates is set to 'nonsecure and secure'. Is there anyway I can have both DHCP sources and still update DNS on the server when it is available?

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What DNS server are the clients configured with when the router gives them a DHCP lease? And are they configured to send DNS updates in their network adapter settings? Is there any reason you wouldn't just have the router provide DHCP at all times? –  Shane Madden Oct 28 '12 at 18:52
    
Router is configured to issue addresses of remote ISPs DNS servers. Network cards are configured to 'Register this connections addresses in DNS'. I think the main reason that I didn't just leave DHCP to the router was because of this issue where DNS on the server doesn't seem to get updated with the latest IP number. –  NickC Oct 28 '12 at 20:51
    
For the clients to update DNS on the server properly, they'll need to be pointing to the server for DNS. Maybe have the router's DHCP point to the server as primary DNS, and the other DNS servers as secondary? –  Shane Madden Oct 28 '12 at 21:10
    
Of course, I can see the problem clearly now. Have set the internal DNS server as the routers Primary DNS and the external ISPs server as Secondary. That seems to work fine. Thanks –  NickC Oct 29 '12 at 10:09
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As Shane stated in his comment, in order for the DHCP clients to update their A records in your internal DNS server they need to be configured to use that DNS server. If they're being assigned ISP DNS servers from the router when they get their ip addresses from the router then they're going to try to register/update their A records with those ISP DNS servers. A network capture of traffic exiting your network will probably confirm that.

If you're having a problem with your internal DNS server that's then making you use the router for DHCP and DNS then the fix is to resolve the problem with the DNS server.

When you say "DNS on the server doesn't seem to get updated with the latest IP number" can you explain what you mean and what the symptomes of the problem are?

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