You can use the following to set this up, and if you want it to be a two way
trust, then do the same steps in the other direction as well;
315053 HOW TO: Configure One-Way Non-Transitive Trusts in Windows 2000
http://support.microsoft.com/?id=315053

Once the trust is set up, you should be able to see accounts in the other
domain available to add to resoruces, and also available as another logon
domain when you logon. The trust basically just opens the door, but doesn't
grant anybody anything, so you will need to go the serverA in domain A and
grant domainB users access to whatever resources you want.
It is fairly common for the domain admins of one domain to be added to the
Local administrators group of the other domain, which will give admins from
either domain ability to add users, etc.
The trust also needs to be set up between the pdc emulators of each
respective domain and they need to be able to resolve each other both ways,
so be sure name resolution is working ok either via dns, lmhosts files, etc.
180094 How to Write an LMHOSTS File for Domain Validation and Other Name
http://support.microsoft.com/?id=180094

--
David Brandt
Microsoft Corporation

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"Sunny" wrote in message
news:61f401c3e5df$55105fb0$a401280a@phx.gbl...
> how is the trust relationship between two forest works?
>
> We have a sister company. They have their own forest and
> domain controllers. We have our's. We want to be able to
> set up link between these two domain in which each domain
> trust user accounts in the other domain to use its
> resources.
>
> Is there any documentation I can look up to be able to
> accomplish this and if it can be done, is it safe or
> recommended?
>
>