Netopia 435 Reference Manual page 237

The Netopia ISDN Router compares the packet's destination IP
address with the routes in its IP routing table. It begins with the
route at the bottom of the list and works up until there's a match or
the route to the default gateway is reached.
When a.b.c.249 is masked by the first route's subnet mask, it
yields a.b.c.248, which matches the network address in the route.
The Netopia ISDN Router uses the connection profile associated
with the route to connect to Router C, and then forwards the packet.
Router C delivers the packet to the host on its local network.
The following diagram illustrates the IP address space taken up by
the two remote IP subnets. You can see from the diagram why the
term nested is appropriate for describing these subnets.
addresses used
by a.b.c.128
addresses used
by a.b.c.248
Understanding IP Addressing
1
128
192
248
254
C-15
Address range
available to
a.b.c.0, less
the two nested
subnets