How to find the Windows DNS style Domain Name

Last updated on 9 February 2016

A common requirement on internal network assessments is to know the fully qualified Windows domain name of the network. This is trivial to obtain if using DHCP.

On Linux like systems simply:

cat /etc/resolv.conf

The domain name is in the ‘domain’ or ‘search’ field.

On Windows you can see the domain name in the Network Settings accessible from the system tray on in the ‘DNS suffix’ section of the output of:

ipconfig

However if for whatever reason you are not using DHCP these methods are less likely to work. But it is possible to get the domain name by querying a host on the network. My preferred method of doing this is, of course, python:

import socket
socket.gethostbyaddr("ip_addr")

Where ip_addr is any live host on the network, the DNS server I act as pot of thestatic configuration is what I usually use. This function returns the full qualified domain name, a list of aliases (commonly the NetBIOS  name), and the IP address of the remote host. Everything after the first ‘.’ in the FQDN is the DNS style Windows Domain Name. E.g. if the FQDN of the host is:

dnsserv1.corp.ad.company.com

the domain name would be:

corp.ad.company.com

There are other methods that may be used to identify the legacy -but ubiquitous – NetBIOS style Windows Doman Name which I will save for a future post.

This information can then be used to identify the Windows Domain Controllers, which I will also describe in a later post.