How to change default source address?

[Lucian at lastdot.org]

Hi guys,

I need to change the default source address on a freebsd server.
My situation is somehow similar to this
(http://marc.info/?l=freebsd-questions&m=122535960804508&w=2).
In linux i can easily do it like:

ip ro replace default via 10.10.10.1 src a.b.c.d (where a.b.c.d is em0 alias).

Any ideas?