There's no easy way to force all the syslog traffic from a Unix machine to a particular facility. And, in fact, if you're trying to do this you're probably not fully grasping the idea of facilities. Use simple 'grep's on the syslog files to figure out what log entries came from what machines.
Brainbench MVP for Unix Administration and Internet Security, SANS Review Editor, and Center for Internet Security HP-UX Benchmark project leader