question about cross-realm auth

[Rainhard Vladyka]

Hello,

I got a general question about this.
I got a A.COM and a B.NET Domain, they both have a two-way trust.
The A.COM dc is behind a firewall and is only available through the  
kdc of B.NET.
Is it possible to authenticate a client at A.COM through the kdc of B.NET?
Or do I missinterpret the behaviour of cross realm authentication.
And If so, is there a way to accomplish that?

thanks in advance
Rainhard