I am pretty new to Linux/networking, so please bear with me.

I have a SLES that I use as a webserver. It has the IP address 10.108.15.133 and subnet mask 255.255.252.0.
I have recently moved this server into my DMZ because I run a web application on this server, and want to keep the server in a different network from my company network.
When I type:
> nslookup XXX
(where XXX is some machine in my company network)
I get the following:

> nslookup XXX
;; connection timed out; no servers could be reached

I have used Yast2 to set my name server to 10.108.11.224, which is the DNS server for the company network.

I understand the cause of this problem could lie in many areas. E.g.:
1. nslookup not configured on the SLES
2. firewall preventing nslookup from using a DNS server sitting in a different network.
3. etc.

Why does nslookup not work from my SLES sitting in the DMZ? Is there any tests that I can do help me identify where the problem lies?

Thanks in advance.

1. I would suspect that firewall prevents the dns traffic to flow freely between DMZ and LAN.
2. I would also check if DNS service is up and running on the nameserver.
Boris.

1. What port do I need to open up to allow dns traffic to flow freely between DMZ and LAN?
2. How do I check if DNS service is up and running on the nameserver?

you need to allow traffic from DMZ to nameserver on LAN on UDP port 53.
the easiest way to find out if dns is working on the nameserver is
dig @localhost hostname
and see if you get a result back
if you are using BIND you can check with
ps -ef|grep [n]amed
and see if the process is running