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Local network DNS problems

W

wirelessenabled

Platinum Member
Starting this past week computers, all XP SP3, on the internal network are unable to access the email server or web server. Users outside the local network have no problems.

Background of our network.

The internal network uses 192.168.x.x for addressing.

There is a DMZ using 10.1.x.x. The email and web servers are in this DMZ.

A Windows Server 2003 box is running as a local DNS server. It contains the A records for the email and web servers, ie mail.x.com 10.1.10.3 and www.X.com 10.1.10.2. This setup has been running for about 3 years.

If I go to a computer on the internal network and do a NSLOOKUP mail.x.com I get the DNS server name and the correct address 10.1.10.3. I also get the correct response for NSLOOKUP www.x.com which is the DNS server name and 10.1.10.2.

However on the same internal computer if I PING mail.x.com then it responds with the external IP address 74.x.x.x. Same if I ping www.x.com, I get the external IP address.

If on the local computer I enter IPCONFIG /registerdns then my pings are correct for a while, 30 minutes to 60 minutes or so. Then they go back to reaching the external IP address, meaning no access to the email server etc.

I turned off the power saving/sleep on the network cards and it made no difference.

What else should I be looking for?

Thanks in advance
 
Sounds like DNS round robin is configured somewhere and both the internal and external addresses are registered in internal DNS.
 
yinan said:
Sounds like DNS round robin is configured somewhere and both the internal and external addresses are registered in internal DNS.
Click to expand...

Thanks for the reply!

I will look for that. There isn't anything on the internal DNS server but I will look around to see if there is any 'legacy" stuff still running.
 
a) This is the main reason you never use "company.com" rather "internal.company.com" or some variation.
b) verify that none of the internal workstations are using outside DNS on the local adapters
c) verify that the DMZ servers are not registering themselves in the interior dns. (they really shouldn't be on the inside domain anyway with those conflicting names)
d) make sure you are not forwarding requests for your domains to the root DNS servers on the web.
 
imagoon said:
a) This is the main reason you never use "company.com" rather "internal.company.com" or some variation.
b) verify that none of the internal workstations are using outside DNS on the local adapters
c) verify that the DMZ servers are not registering themselves in the interior dns. (they really shouldn't be on the inside domain anyway with those conflicting names)
d) make sure you are not forwarding requests for your domains to the root DNS servers on the web.
Click to expand...

Did b,c,d.

Found one more workstation doing b. Fixed that.

Now it works for a longer time than before but still eventually gets screwed up. I am in the process of rechecking everything. I must be overlooking a setting somewhere.
 
Make sure your DHCP server isn't handing out external DNS servers. Make sure someone didn't throw a second DHCP server on the network (wireless router, for instance) that's handing out external DNS servers.
 
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