3Com SuperStack 4 Configuration Manual page 101

Routing Management
Policy
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 configuration, as shown 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 2.
Figure 29 The routing table
16.0.0.2 16.0.0.2
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
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
R1 R1 12.0.0.2 12.0.0.2
14.0.0.1 14.0.0.1
12.0.0.3 12.0.0.3
The Switch 5500G-EI supports the configuration of a series of dynamic routing
protocols such as RIP and OSPF, as well as static routes. The static routes
configured by the user are managed together with the dynamic routes as detected
by the routing protocol. The static routes and the routes learned or configured by
routing protocols can be shared with each other.
Routing Protocols and Route Preferences
Routing protocols (including static configurations) can generate different routes to
the same destination, but not all these routes are optimal. In fact, at a certain
moment, only one routing protocol can determine a current route to a single
destination. Thus, each routing protocol (including static configurations) has a set
preference, and when there are multiple routing information sources, the route
with the highest preference becomes the current route. Routing protocols and the
default preferences of the routes that they learn are shown in
smaller the value, the higher the preference).
Table 107 Routing Protocols and the Default Preferences for Routes
Routing protocol or route type
DIRECT
OSPF
ISIS
STATIC
RIP
OSPF ASE
OSPF NSSA
16.0.0.3 16.0.0.3
16.0.0.0 16.0.0.0
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
10.0.0.1 10.0.0.1
3 3
R8 R8
13.0.0.0 13.0.0.0
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 preference of the corresponding route
0
10
15
60
100
150
150
IP Routing Protocol Overview
Figure 29, the number in
The routing table of router R8 The routing table of router R8
Destination Destination Forwarding Forwarding
host host
router router
location location
10.0.0.0 10.0.0.0 Directly Directly
2 2
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
13.0.0.0 13.0.0.0 Directly Directly
14.0.0.0 14.0.0.0
13.0.0.2 13.0.0.2
15.0.0.0 15.0.0.0 10.0.0.2 10.0.0.2
16.0.0.0 16.0.0.0 10.0.0.2 10.0.0.2
Table
113
Port Port
passed passed
2 2
1 1
1 1
3 3
3 3
2 2
2 2
107. The