Справочное Руководство для Netopia 430 s

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Understanding IP Addressing
C-15
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 for wards 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.
1
254
Address range
available to
a.b.c.0, less
the two nested
subnets
248
addresses used
by a.b.c.248
192
128
addresses used
by a.b.c.128