Routing table information, Dynamic routing protocols – H3C Technologies H3C SecBlade NetStream Cards User Manual
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Routing table information
You can view the brief information of a routing table by using the display ip routing-table command.
For example:
Routing Tables: Public
Destinations : 7 Routes : 7
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.0/24 Direct 0 0 1.1.1.1 GE0/2
2.2.2.0/24 Static 60 0 12.2.2.2 GE0/3
80.1.1.0/24 OSPF 10 2 80.1.1.1 GE0/4
…(Part of the output information is omitted)
A route entry includes the following key items:
•
Destination—Destination IP address or destination network
•
Mask—The network mask specifies, in company with the destination address, the address of the
destination network. A logical AND operation between the destination address and the network
mask yields the address of the destination network. For example, if the destination address is
129.102.8.10 and the mask 255.255.0.0, the address of the destination network is 129.102.0.0. A
network mask is made up of a certain number of consecutive 1s. It can be expressed in dotted
decimal format or by the number of the 1s.
•
Pre—Preference of the route. Among routes to the same destination, the one with the highest
preference is optimal.
•
Cost—When multiple routes to a destination have the same preference, the one with the smallest
cost becomes the optimal route.
•
NextHop—Specifies the IP address of the next hop
•
Interface—Specifies the interface through which a matching IP packet is to be forwarded
Dynamic routing protocols
Based on dynamic routing protocols, dynamic routing can detect network topology changes and
recalculate the routes, so it is suitable for large networks. However, dynamic routing is difficult to
configure. It not only imposes higher requirements on the system, but also consumes a certain amount of
network resources.
Dynamic routing protocols can be classified based on different criteria, as shown in
:
Table 9 Dynamic routing protocols
Criterion Categories
Optional scope
•
Interior gateway protocols (IGPs)—Work within an autonomous system (AS).
Examples include RIP, OSPF, and IS-IS.
•
Exterior gateway protocols (EGPs)—Work between ASs. The most popular one is
BGP.
Routing algorithm
•
Distance-vector protocols—RIP and BGP. BGP is also considered a path-vector
protocol.
•
Link-state protocols—OSPF and IS-IS