IP address lookup of AD domain server

Wanted to find IP address of active domain server, from command prompt type:

nslookup    
set type=all
_ldap._tcp.dc._msdcs.DOMAIN_NAME

From Serverfault

Join Apple OS to Windows domain

To join computer with Apple OS to Windows domain, goto system preferences, user accounts:

Click the Lock to make changes to these settings. Then click the Join button next to Network Account Server

Now click the Open Directory Utility button

You should now be at the Directory Utility; click the Lock to make changes. Then make sure Active Directory is checked, highlight it, and then click the Pencil to edit this setting.

Here you can enter your domain information and computer ID. For this example the domain is hq.test.us and the computer ID is Mac. The computer ID is the computer name that will show up in Active Directory once the Mac is joined to the domain.

Click the arrow to Show Advanced Options. This gives you 3 extra options you can configure. To keep it simple I usually leave these settings default except for the Administrative section. Click the Administrative button and enter the IP address or the FQDN of your domain controller in the Prefer this domain server section. For this example I used the IP address of my domain controller 192.168.1.172. You can also specify groups that are allowed administration privileges.

Now click the Bind button and you will be prompted for credentials. Enter your domain administrator username and password and click OK.

You should see it progress through steps 1-5 as you are authenticated and joined to the domain.

https://www.pluralsight.com/blog/tutorials/join-mac-to-windows-domain