Routing table

A RIB contains the global routing information and related information, including route recursion, route redistribution, and route extension information. The router selects optimal routes from the routing table and puts them into the FIB table. It uses the FIB table to forward packets. For more information about the FIB table, see Layer 3—IP Services Configuration Guide.

Table 1 categorizes routes by different criteria.

Table 1: Route categories

Criterion	Categories
Destination	Network route—The destination is a network. The subnet mask is less than 32 bits. Host route—The destination is a host. The subnet mask is 32 bits.
Whether the destination is directly connected	Direct route—The destination is directly connected. Indirect route—The destination is indirectly connected.
Origin	Direct route—A direct route is discovered by the data link protocol on an interface, and is also called an interface route. Static route—A static route is manually configured by an administrator. Dynamic route—A dynamic route is dynamically discovered by a routing protocol.

To view brief information about a routing table, use the display ip routing-table command.

<Sysname> display ip routing-table

Destinations : 9        Routes : 9

Destination/Mask   Proto   Pre Cost        NextHop         Interface
0.0.0.0/32         Direct  0   0           127.0.0.1       InLoop0
3.3.3.3/32         Direct  0   0           127.0.0.1       InLoop0
127.0.0.0/8        Direct  0   0           127.0.0.1       InLoop0
127.0.0.0/32       Direct  0   0           127.0.0.1       InLoop0
127.0.0.1/32       Direct  0   0           127.0.0.1       InLoop0
127.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0
...

A route entry includes the following key items:

Destination—IP address of the destination host or network.
Mask—Mask length of the IP address.
Proto—Protocol that installed the route.
Pre—Preference of the route. Among routes to the same destination, the route with the highest preference is optimal.
Cost—If multiple routes to a destination have the same preference, the one with the smallest cost is the optimal route.
NextHop—Next hop.
Interface—Output interface.

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