3Com 7757 Configuration Manual page 282

282 C 31: IP R
HAPTER OUTING
P O
ROTOCOL VERVIEW
routes. The one with the highest preference (the smallest numerical value) will
be selected as the current optimal route.
According to different destinations, routes fall into the following categories:
Subnet route: The destination is a subnet.
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Host route: The destination is a host.
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In addition, according to whether the network where the destination resides is
directly connected to the router, routes falls into the following categories:
Direct route: The router is directly connected to the network where the
■
destination resides.
Indirect route: The router is not directly connected to the network where the
■
destination resides.
In order to avoid an oversized routing table, you can set a default route. All the
packets for which the router fails to find a matching entry in the routing table will
be forwarded through this default route.
As shown in Figure 68, the number in each network cloud indicates the network
address and "R" represents a router. Router G is connected to three networks, and
so it has three IP addresses and three physical ports. Its routing table is shown in
Figure 68.
Figure 68 Routing table
Router A
13.0.0.1
11.0.0.1
11.0.0.0
11.0.0.2
14.0.0.1
Router B
12.0.0.1
12.0.0.0
12.0.0.2
15.0.0.1
Router C
13.0.0.2
13.0.0.0
13.0.0.3
Router D
14.0.0.2
14.0.0.3
14.0.0.0
14.0.0.4
Router E
15.0.0.3
15.0.0.2
15.0.0.0
Router F
16.0.0.1
16.0.0.0
16.0.0.2
Router G
17.0.0.1
17.0.0.0
17.0.0.2
Router H