Trust agains forests with multiple domain controllers

Posted on 2013-06-23
Medium Priority
Last Modified: 2013-06-26
If I want to setup a trust between to forests with a single DC in each forest, then it's pretty much out of the box.

But what if there are multiple DC's in each forest?

I have two forest:
A: Two DC's (Windows Server 2008 R2)
B: Four DC's (Two Windows Server 2008 R2 / Two Windows Server 2012)

How do I setup the trust between theese two forests?
Must I take the necessary steps on all DC's or can it be done on one DC in each forest?

Question by:Kasper Katzmann
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LVL 15

Accepted Solution

Rob Stone earned 2000 total points
ID: 39269448
You just make the trust using AD Domains & Trusts from a DC or a client with the admin tools installed.

The number of DC's in each forest isn't relevant.


Author Comment

by:Kasper Katzmann
ID: 39269457
How about port openings (53, 88, 389, 445, 636)? Will they have to be made between each DC?
LVL 17

Expert Comment

ID: 39269470
You will need to open all the below ports.

123/UDP      W32Time
135/TCP      RPC Endpoint Mapper
464/TCP/UDP      Kerberos password change
49152-65535/TCP      RPC for LSA, SAM, Netlogon (*)
389/TCP/UDP      LDAP
636/TCP      LDAP SSL
3268/TCP      LDAP GC
3269/TCP      LDAP GC SSL
53/TCP/UDP      DNS
49152 -65535/TCP      FRS RPC (*)
88/TCP/UDP      Kerberos
445/TCP      SMB
49152-65535/TCP      DFSR RPC (*)


Author Comment

by:Kasper Katzmann
ID: 39269546
There should have been a "and so on" after my litlle listing.

But what about which server the openings should be between. All the DC's or...?
LVL 15

Expert Comment

by:Rob Stone
ID: 39269654
Generally you create a firewall rule on both sides (on the externally facing firewall).  Once that's configured, you then need to go through the checklist in the first hyperlink. If you are having issues, check the network logs on the firewalls to see if anything is still getting blocked.

If you use Windows Firewall on the servers, when you install the role the relevant ports should open automatically.  I'm not sure if that's the case if you use a 3rd party firewall.

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