Running vastool search without any switch will search the domain in which Quest Authentication Services (QAS/VAS) has been joined to. It is possible to search an alternate domain using vastool.
If you have multiple trusted domains use the -b switch and specify the search base of the alternate domain. See below for examples.
This will search the alternate domain for computer objects matching the operating system Linux:
# vastool -u host/ search -b DC=DomainB,DC=com (&(objectclass=computer) (operatingSystem=Linux)) operatingsystem
This will search the alternate domain for a UID that matches 1001:
# vastool -u host/ search -b DC=DomainB,DC=com uidNumber=1001
You may also refer to the man page for vastool and refer to the search option. Also, typing in vastool search without any options or criteria will display its usage.