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Two Way Trusts

I have two domains. a.local and b.local.  They are separate domains and forests.  I need to create a trust between the two domains.  They are both 2003 domains.  I am migrating b into a, so I will probably need to create a new site in the a domain.  Can someone please give me some guidance on how to do this and in what order?  Thanks.
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1 Solution
good info here:


Did you want a two way, one way, domain wide or forest wide trust?
If you are trying to migrating b to a, then you really need to create a one-way trust that b trusts a. But depending on what other tasks you need to do between these two domain and if not reason you can have two way trust, you should create a two-way trust. As far as "create a new site in the a domain", this has nothing to do with trust and migration, if you are referring to active directory sites.
Here's an example of how to create the two way trusts:
Scenarios, just an example:
Note: you can start either on a.local or  b.local, the order of creation for the trust doesn't matter.
New Trust-->DNS or NetBIOS name of other domain-->External Trust-->Two-Way-->This Domain only--> Domain-Wide Authentication-->Trust Password-->No Need to confirm any trust at the moment

New Trust-->DNS or NetBIOS name of other domain-->Two-Way-->This Domain only-->Domain-Wide Authentication-->Trust Password-->No Need to confirm any trust at the moment

Note on authentication method when creating the trust:
If you want to create trust but do not wish to open all your servers and workstations for users in other domain by default, configure with Selective authentication.
If you want to create trust and wish to allow users from other domain to access any resources opened to "everyone" or "authenticated users" group by default, configure with Domain-wide authentication.
Also, if security is not a concen between these two forests(networks), then you can have your firewall wide open otherwise, you need these ports and protocol opened before creating the trust:

These are the ports and protocol require to open on both side of the firewall if trust is to be established between two domains:

UDP      135, 389, 53, 88, 445, (for NetBIOS: 137, 138)
TCP       135, 389, 636, 53, 88, 445, 1024-65535, (for NetBIOS: 139, 42)
ICMP      Dependency of port 139, also used by Windows Redirectors, Group Policy, MTU etc

Service Name             UDP       TCP
LDAP                   389       389
LDAP SSL             N/A       636
RPC Endpoint Mapper       135       135
Global Catalog LDAP       N/A       3268
Global Catalog LDAP SSL N/A       3269
Kerberos             88       88
BTW, one thing you must verify before creating the trust is to make sure DNS name resolution is working from the domain controllers between the two domains in the forests.
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