Merging 2 domains with same NetBIOS domain name

Copper Contributor

This is the current situation at a new company I started with:

There are two locations with separate AD's: 

  • location one -
  • location two - location2.local

One Office 365 Business Premium tenant

  • connected to AD location2.local via AAD Connect w/ Password Hash Sync
  • userPrincipalName - (SMTP address)
  • AD is not connected, but users are manually created in Office 365 (local AD and Office are separate user accounts).

The plan is to create a new Forest and migrate EVERYTHING to that

So basically the super simplify plan is,

  • disconnect the sync,
  • create new forest
  • join domains to new forest
  • migrate everything using ADMT to new forest
  • reconnect to original O365 tenant

My problem is location2.local has the netbios domain name COMPANY and I'd like to use this netbios name for the new domain. From what I've read, having 2 domains with the same netbios domain name will cause problems. If this is true how do I get around this, or what is my best option?

1 Reply
That will be a problem as its pretty common knowledge if you plan to use ADMT there will need to be a trust and AFAIK you can't do that if the NetBIOS name is the same.


Some ways you could get around this.

1.) Go with a new NetBIOS name (I.e. COMPANYNEW)
2.) Consolidate onto then move to
3.) Take everything out on location2.local and then build from scratch (not recommended but it's an option)

I wouldn't say that there is any 'best' option as such. It's the best of a worst bunch as you are cleaning up here. If I took a short term view having a new NetBIOS name is easiest. If I took a very long term view and want it to be exactly by the book I would probably at least consider 2 or 3. However, that's a lot of work potentially.

It is important because you shouldn't change it once set. There is workarounds to change it but changing the name after its implemented will mean you won't be supported after.

Best, Chris