NetBIOS vs. FQDN

Question

Hi! I've got an issue when accessing a web site, I can access it by using the NetBIOS name, but when accessing with the FQDN i get an error.

Any ideas on how to troubleshoot this?

(There is no DNS configured yet, we have modified the Hosts file to enter the related names and IP.)

Answer 1

Just to make sure, you have something like this

192.168.100.5 othermachine othermachine.mydomain.local

with both the netbios and the FQDN in it and not just the IP and netbios name?

Answer 2

Assuming, as dragonmantank mentioned above, that the FQDN is in your hosts file, I'd look at whether the web server software itself is configured to accept requests with the FQDN in the Host field.

Answer 3

First, check the obvious: are there any typos in the file?

Next, test out the name resolution. Something simple like pinging the web server by it's FQDN will do. See if the right IP is mentioned.

• If you get "unknown host", your client's hosts file does not have an entry for the FQDN you entered (check for typos in the host name), or, for some reason, your computer isn't reading your hosts file.
• If you get the wrong IP address, then you have the wrong IP in your hosts file (check for typos in the IP address), your computer's DNS cache is polluted (try: ipconfig /flushdns on a Windows machine), or something else is overriding the lookup (duplicate entries in the hosts file?).

Next up, try communicating with your web server. Using Telnet, speak HTTP to it, and see how it responds:

telnet 192.168.0.1 80

Substitute your web server's IP address instead of 192.168.0.1. Provide the following lines:

GET / HTTP/1.1
Host: fqdn.mywebserver.com

Try the server's IP, server's netbios name, and finally the server's FQDN in place of fqdn.mywebserver.com. Be sure to press return twice after entering the host header.

If the response is different between the netbios name and the FQDN, then it's a web server configuration issue; you need to adjust you virtual host settings (in Apache, the ServerAlias directive should be used to add additonal names. In IIS its in Web Site (tab) -> Advanced (button)).

After that... I'm really out of ideas.