Multiple default routes on multihome host

[Nick Barnes]

I have a multi-home host: more than one IP address.  The addresses are
in separate subnets but run over the same ethernet segment (this is a
temporary situation while I switch an office network over from one
network provider to another).

I want packets from address A1 to be sent via gateway G1, but packets
from address A2 to be sent via gateway G2.

How do I do this?  Can I just have more than one default route?  I'm
remote from the machine in question, so I don't want to tinker with
the default route until I'm sure of the answer.

Thanks in advance,

Nick Barnes