3Com 10014298 manual Routing Table

IP Routing Protocol Overview 83

■The output interface — Indicates an interface through which an IP packet should be forwarded.

■The next hop address — Indicates the next router that an IP packet will pass through.

■The priority added to the IP routing table for a route — Indicates the type of route that is selected. There may be multiple routes with different next hops to the same destination. These routes can be discovered by different routing protocols, or they can be the static routes that are configured manually. The route with the highest priority (the smallest numerical value) is selected as the current optimal route.

Routes are divided into two types: subnet routes, in which the destination is a subnet, or host routes, in which the destination is a host.

In addition, depending on whether the network of the destination host is directly connected to the router, there are two types of routes:

■Direct route: The router is directly connected to the network where the destination is located.

■Indirect route: The router is not directly connected to the network where the destination is located.

To limit the size of the routing table, an option is available to set a default route. All the packets that fail to find a suitable table entry are forwarded through this default route.

In a complicated Internet, as shown in the following figure, the number in each network is the network address. The router R8 is connected to three networks, so it has three IP addresses and three physical ports. Its routing table is shown in Figure 23.

Figure 23 The Routing Table

16.0.0.3

16.0.0.216.0.0.3

15.0.0.2		16.0.0.0	R7	10.0.0.2
	R6
15.0.0.0	16.0.0.2	R5	10.0.0.0
	13.0.0.2	13.0.0.3
			10.0.0.1
15.0.0.1		13.0.0.0		R8
R2			11.0.0.1
14.0.0.2
		13.0.0.4
				11.0.0.0
14.0.0.0	13.0.0.1
		R3
	12.0.0.2		11.0.0.2
14.0.0.1	R1
			R4

12.0.0.312.0.0.0 12.0.0.1

Destination	Forwarding	Port
host	router	passed
location
	Directly	2
10.0.0
11.0.0	Directly	1
12.0.0	11.0.0.2	1
13.0.0	Directly	3
14.0.0	13.0.0.2	3
15.0.0	10.0.0.2	2
16.0.0	10.0.0.2	2

Routing Management The Switch 7750 supports the configuration of a series of dynamic routing Policy protocols such as RIP, as well as static routes. The static routes configured by the