Sorry I'm not man enough...err savvy enough to know the man page ways to write the needed lingo.
Could somebody update the man page for route with the following gist: In a change or add command where the destination and gateway are not suf- ficient to specify the route, the -ifp or -ifa modifiers may be used to determine the interface or interface address. + -ifa specifies an interface by its IP address (not name). + + -ifp specifies an interface by name and link layer address: + + -ifp interface name:link layer address + + example: + + route add 192.1.2.3 10.10.0.34 -ifp em0:08:00:69:ff:ff:ff dmo