Netopia 4753 2A4NA Administration Manual page 252

B-12 Administration Guide
Routers B and C (which could also be Netopia 4753s) serve the two remote networks that are subnets of
a.b.c.0. The subnetting is accomplished by configuring the Netopia 4753 with connection profiles for Routers B
and C (see the following table).
Connection profile
For Router B
For Router C
The Netopia 4753's connection profiles for Routers B and C create entries in its IP routing table. One entry
points to the subnet a.b.c.128, while a second entry points to the subnet a.b.c.248. The IP routing table might
look similar to the following:
Network Address-Subnet Mask-----via Router------Port------------------Type----
----------------------------------SCROLL UP-----------------------------------
0.0.0.0
127.0.0.1
a.b.c.128
a.b.c.248
---------------------------------SCROLL DOWN----------------------------------
UPDATE
Let's see how a packet from the Internet gets routed to the host with IP address a.b.c.249, which is served by
Router C. The packet first arrives at Router A, which delivers it to its local network (a.b.c.0). The packet is then
received by the Netopia 4753, which examines its destination IP address.
The Netopia 4753 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 4753 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.
Remote IP address
a.b.c.128
a.b.c.248
IP Routing Table
0.0.0.0 a.b.c.1
255.255.255.255 127.0.0.1
255.255.255.192 a.b.c.128
255.255.255.248 a.b.c.248
Remote IP mask
255.255.255.192
255.255.255.248
--
Loopback
WAN
WAN
Bits available for host
address
7
3
Other
Local
Local
Local