Windows – DNS Conditional forwarder returns NETBIOS instead of FQDN

conditionaldomain-name-systemforwardingwindows

Strange DNS problem for which I hope you can help.

Active Directory with NETBIOS name "Shortdomain" and as FQDN "verylongdomainname.lan". Domain controller DC01 behind firewall. IP: x.x.x.1

Customer site, connected over VPN. Customer has local DNS Server. On their DNS Server I wanted to create a new conditional forwarder zone. In DNS manager I enter "verylongdomainname.lan" and when I enter IP x.x.x.1 I first get a timeout but after the timeout it shows the NETBIOS name "Shortdomain" where I would have expected the FQDN name for the server. I then click OK and the zone is added.

On any server in customer site, I fail to resolve any server in "verylongdomainname.lan", but when I start nslookup and then run the command "Server x.x.x.1", I successfully connect to the DNS server and I am then able to resolve all server names in the "verylongdomainname.lan" domain. To me this proves routing and firewalling is permitting a connection from customer to DNS Server x.x.x.1. Correct ???

Any idea why the conditional forwarding is not working and how to fix it?

From the command line:

    command: nslookup
    result: y.y.y.5 

    command: server1.verylongdomainname.lan 
    result: domain not found 

    command: server x.x.x.1 
    result: server (x.x.x.1) 

    command: server1.verylongdomainname.lan
    result: server1.verylongdomainname.lan x.x.x.7 (which is correctly resolved)

Best Answer

Turned out that the customer DNS Servers itself weren't able to access my DNS Servers. Some NAT rule on customer side wasn't correct. Thanks for the tips!