3Com Switch 8800 Advanced Software V5 Configuration Guide
Routing Protocol Overview 189
Routing Protocol
Overview
Static Routing and
Dynamic Routing
Static routing is easy to configure and requires less system resources. It works well
in small, stable networks with simple topologies. Its major drawback is that you
must perform routing configuration again whenever the network topology
changes; it cannot adjust to network changes by itself.
Dynamic routing is based on dynamic routing protocols, which can detect network
topology changes and recalculate the routes accordingly. Therefore, dynamic
routing is suitable for large networks. Its disadvantages are that it is complicated
to configure, and that it not only imposes higher requirements on the system, but
also eats away a certain amount of network resources.
Classification of
Dynamic Routing
Protocols
Dynamic routing protocols can be classified based on the following standards:
Operational scope
■ Interior Gateway Protocols (IGPs): Work within an autonomous system,
typically include RIP, OSPF, and IS-IS.
■ Exterior Gateway Protocols (EGPs): Work between autonomous systems. The
most popular one is BGP.
n
An autonomous system refers to a group of routers that share the same routing
policy and work under the same administration.
Routing algorithm
■ Distance-vector protocols: Include mainly RIP and BGP. BGP is also considered a
path-vector protocol.
■ Link-state protocols: Include mainly OSPF and IS-IS.
The main differences between the above two types of routing algorithms lie in the
way routes are discovered and calculated.
Type of the destination address
■ Unicast routing protocols: Includes RIP, OSPF, BGP, and IS-IS.
■ Multicast routing protocols: Includes PIM-SM and PIM-DM.
Destination Network Nexthop Interface
10.0.0.0 10.0.0.1 2
11.0.0.0 11.0.0.1 1
12.0.0.0 11.0.0.2 1
13.0.0.0 13.0.0.4 3
14.0.0.0 13.0.0.2 3
15.0.0.0 13.0.0.2 3
16.0.0.0 10.0.0.2 2