Can an interface be restricted?

[DonDavisFCB]

I have two ethernet interfaces on the same subnet.
en1 is to receive syslog traffic only.
en0 is for all other traffic.

How can I prevent en1 from being discovered and used for 10.0.108 outbound traffic?
It seems to be round-robin'ing...
These are the entrys in my static routes list
10.0.108/24 10.0.108.19 U 2067 92678639 en0 - - =>
10.0.108/24 10.0.108.119 U 7 92933437 en1 - -

Another question...
What is the "no" option to prevent every address in my arp cache from becoming a static route?

Thanks