You can check which DiRT machines are entered in the department's netgroup by going to capefear (where the department's master yp server is) and doing
ypcat -k netgroup | grep dirt
and then filtering the output any way you'd like it.
An even better way, however, is to look directly at the netgroup file itself
/var/adm/util/tables/netgroups/netgroup
which was recently made readable to us by John Sopko. (Thanks!)