backup default routes

[Ezra Banoba]

Hello,
I have a gatway box running freebsd 4.8 and several links to the internet
via different ISP's.
This box is connected directly to one of the ISP's but also has access to
the other gatways via the LAN.
I would like to setup static backup (default) routes such that when and if
the main link goes down, the default route for this box is automatically
changed to point to another router on the LAN.I am having trouble
implementing this on freebsd.
Any ideas?

Ezra Banoba
Systems Administrator/Programmer
Computer Froniters International
Plot 32 Lumumba Avenue
www.cfi.co.ug
+256 031260485