RADIX_MPATH usage information

[Brett Glass]

A customer has asked me how to multihome a machine. I was going to 
give him the standard response regarding policy routing and "fwd" 
rules in FreeBSD's IPFW, but then remembered that the RADIX_MPATH 
option is supposed to be implemented in FreeBSD 8.1.

Is there documentation on the use of this kernel option? How can 
multiple gateways be specified in rc.conf? What else does one need 
to know simply to answer requests (say, for a Web server) via the 
gateway through which they arrived? To do load balancing? Is there 
a HOWTO or man page? (I couldn't find one, but may have missed it.)

--Brett Glass