3Com 8807 Configuration Manual page 281

Next hop address: It indicates the IP address of the next router that an IP packet
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will pass through.
Priority added to the IP routing table for a route: There may be different next
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hops to the same destination. These routes may be discovered by different
routing protocols, or they can just be the static routes configured manually. The
one with the highest priority (the smallest numerical value) will be selected as
the current optimal route.
Path cost: Cost to forward data over the route.
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According to different destinations, the routes can be divided into:
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 of the destination host is directly
connected to the router, there are the following types of routes:
Direct route: The router is directly connected to the network where the
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destination resides.
Indirect route: The router is not directly connected to the network where the
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destination resides.
In order to limit the size of the routing table, an option is available to set a default
route. All the packets that fail to find the suitable entry will be forwarded through
this default route.
In a complicated Internet as shown in Figure 70, the number in each network is
the network address, and R stands for a router. The router R8 is directly connected
with three networks, so it has three IP addresses and three physical ports, and its
routing table is shown in the diagram below:
Figure 70 The routing table
16.0.0.2 16.0.0.2
16.0.0.0 16.0.0.0
15.0.0.2 15.0.0.2
R 6 R 6
16.0.0.2 16.0.0.2
15.0.0.0 15.0.0.0
13.0.0.2 13.0.0.2
15.0.0.1 15.0.0.1
13.0.0.0 13.0.0.0
R2 R2
14.0.0.2 14.0.0.2
13.0.0.1 13.0.0.1
14.0.0.0 14.0.0.0
12.0.0.2 12.0.0.2
R1 R1
14.0.0.1 14.0.0.1
12.0.0.3 12.0.0.3
The 3Com Switch 8800 Family Series Routing Switches (hereinafter referred to as
Switch 8800 Family series) support the configuration of a series of dynamic
routing protocols such as RIP, OSPF, IS-IS and BGP, as well as the static routes. In
Introduction to IP Route and Routing Table
16.0.0.3 16.0.0.3
R7 R7
10.0.0.2 10.0.0.2
R5 R5
10.0.0.0 10.0.0.0
13.0.0.3 13.0.0.3
2 2
10.0.0.1 10.0.0.1
3 3
R8 R8
1 1
13.0.0.4 11.0.0.1 13.0.0.4 11.0.0.1
11.0.0.0 11.0.0.0
R3 R3
11.0.0.2 11.0.0.2
R4 R4
12.0.0.0 12.0.0.0
12.0.0.1 12.0.0.1
The routing table of router R8 The routing table of router R8
Destination Destination Forwarding Forwarding Port Port
host host
passed passed
router router
location location
2 2
10.0.0.0 10.0.0.0 Directly Directly
1 1
11.0.0.0 11.0.0.0 Directly Directly
12.0.0.0 12.0.0.0 11.0.0.2 11.0.0.2 1 1
Directly Directly
13.0.0.0 13.0.0.0 3 3
14.0.0.0 14.0.0.0
13.0.0.2 13.0.0.2 3 3
15.0.0.0 15.0.0.0 10.0.0.2 10.0.0.2 2 2
2 2
16.0.0.0 16.0.0.0 10.0.0.2 10.0.0.2
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