If you set default routing to "on" or "listen" on the PortMaster and
it hears a default route via RIP with a lower metric than the static
gateway, it uses the learned gateway. If it doesn't have a static gateway
it'll use whichever dynamically learned gateway that has a lower metric,
and if the one it chooses goes away, after 120 seconds it should start
using the other route instead.
All this will actually be explained in the upcoming 2nd edition of
"Configuration Guide for PortMater Products", along with everything
else anyone ever wanted to know about routing on a PortMaster.
-- Carl