Active Directory: Creating a Cross Forest Transitive Trust

To create a forest trust

1. Open Active Directory Domains and Trusts.
2. In the console tree, right-click the domain node for the forest root domain, and then click Properties.
3. On the Trust tab, click New Trust, and then click Next.
4. On the Trust Name page, type the DNS name (or NetBIOS name) of another forest, and then click Next.
5. On the Trust Type page, click Forest trust, and then click Next.
6. On the Direction of Trust page, do one of the following:
   • To create a two-way, forest trust, click Two-way.
     Users in this forest and users in the specified forest can access resources in either forest.
   • To create a one-way, incoming forest trust, click One-way:incoming.
     Users in the specified forest will not be able to access any resources in this forest.
   • To create a one-way, outgoing forest trust, click One-way:outgoing.
     Users in this forest will not be able to access any resources in the specified forest.
7. Continue to follow the wizard.

 

* Reference: http://technet.microsoft.com/en-us/library/cc780479(WS.10).aspx

Useful Troubleshooting Commands

When cross-forest trusts fail, the secure channel should be verified to determine that a foreign DC can be identified and contacted. This post provides information on troubleshooting techniques in this scenario, and is really only the first step in troubleshooting - establishing that there are no DC locator issues determining what should be a valid DC across the trust.
The following commands are useful for troubleshooting secure channel issues, specifically name resolution, DC locator and connectivity:

· nltest /domain_trusts /v

· nltest /sc_query:%trusted_domain%

· nltest /sc_reset:%trusted_domain%[\%DCname%]

· nslookup -debug -type=srv _ldap._tcp.dc._msdcs.%domainFQDN%