2003 Server DNS Problem

I have an old 2003 server (S1) that has been my acting webserver. I have just added a second 2003 server (S2) to use as an ad server. I am trying to set it up so that when I navigate to ads.mydomain.com, it will get forwarded over to S2.

I have gone into the DNS console on S1 and added an A record that points to the external IP address of S2. When I remote onto S1 (whose DNS points to itself) and navigate to ads.mydomain.com, it forwards the request properly to S2 and the ad server site comes up. When I try this from any other workstation, it will not forward the request correctly. It just takes me mydomain.com instead. I have found that this is the behavior that happens when you put in any random string that is not a valid sub domain. The machine does not know what to do with an invalid sub domain and just returns the main domain site.

Does anyone have any idea why it is working if I try it on a machine that points its DNS to S1, but it does not work when using my ISP's DNS servers?
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You need to clarify a few things..

1. Is S1 an outward facing DNS server? Eg: do you want computers outside of your private network to be able to resolve hosts for yourdomain.com? If you do, you will need to add your dns server as a nameserver for your domain, and forward all port 53 traffic from your outside network to your dns server on your router.

2. IF this is for internal network use, verify to make sure the DNS settings on the workstations are set correctly. Make sure that your server 1 is listed in the DNS settings for your client

3. Finally. paste the output of the following commands on a windows 2000/xp/vista workstation:

ipconfig /flushdns
nslookup ads.mydomain.com
dale_abramsAuthor Commented:
S1 is an outward facing DNS server. I can put S1's external address into my workstation's DNS and it will resolve to ads.mydomain.com correctly. When I switch my DNS settings back to my ISP's, then it just resolves to the homepage on mydomain.com.

The results of running the nslookup are:
*** Can't find server name for address (internal IP of S1): Non-existent domain
*** Default servers are not available
Server:  UnKnown
Address:  (the internal IP of S1)

Name:    ads.mydomain.com
Address:  (the external IP of S2)
dale_abramsAuthor Commented:
The above results for the nslookup are when I pointed my workstations DNS settings at the internal IP address of S1.
Here are the results when I point them at my ISP's DNS server:

Server:  dnsr1.sbcglobal.net

Non-authoritative answer:
Name:    ads.mydomain.com
Address:  (the external IP address of S1)
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dale_abramsAuthor Commented:
I have now added the necessary reverse lookup info to S1 so that when I do the nslookup above on S1, it does not give me the non-existent domain error anymore. I still cannot get to ads.mydomain.com externally though.
dale_abrams: correct! you wont be able to get to ads.mydomain.com externally until the following conditions are met:

1. mydomain.com nameservers are set to the external IP address of your router/server
2. if you are using NAT, port 53 is enabled TCP/UDP and forwarded to the internal IP of your server
3. if S1 has an external IP address, make sure that DNS is listening on that IP and that it is unblocked by all firewalls for port 53 TCP/UDP traffic.

once you have met these conditions, you will need to allow up to 48 hours for DNS to propagate through the internet and your upstream DNS servers to clear their cache.

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dale_abramsAuthor Commented:
I had set everything else up, but I did not add the A record to my nameservers. Thanks for the hellp.
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Windows Server 2003

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