Domains and trusts

Hi,
This is the situation:
1 domain that is currently online. Win2K DC running DNS-veritas
backup-dhcp-mailserver. Range 192.168.206.x/24
They bought new company, nextdoor. We start from scratch, with new domain.
WinSBS2003 DC running DHCP-DNS aswell.
They want veritas backup from site 1 to backup all data from 1 & 2. A
networkcable between 2 buildings is possible, already there, not connected.
(30m length).
I can put trust between domains, but afraid clients from site1 will get ip
from server site 2 and visa versa.
What is the best sollution to interconnect 2 sites so server 1 2K can backup
data from server 2 sbs?
(thought about 2nd nic in both servers and make seperate network between
them?)

Thanks for the advice !

Regards;

Frank
MS SBS2003 SPECIALIST