Multicast; Routing Protocol Overview; Static Routing And Dynamic Routing; Classification Of Dynamic Routing Protocols - 3Com 4500 Configuration Manual

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. It cannot adapt itself to any network topology change automatically so
that you must perform routing configuration again whenever the network topology changes.
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. It is
complicated to configure, and it not only imposes higher requirements on the system than static routing,
but also occupies 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 including RIP,
OSPF, and IS-IS.
Exterior Gateway Protocols (EGPs): Work between autonomous systems. The most popular one is
BGP.
An autonomous system refers to a group of routers that share the same route policy and work under the
same administration.
Routing algorithm
Distance-vector protocols: RIP and BGP. BGP is also considered a path-vector protocol.
Link-state protocols: 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: RIP, OSPF, BGP, and IS-IS.
Multicast routing protocols: PIM-SM and PIM-DM.
This chapter focuses on unicast routing protocols. For information on multicast routing protocols, refer
to the part discussing Multicast.

Routing Protocols and Routing Priority

Different routing protocols may find different routes (including static routes) to the same destination.
However, not all of those routes are optimal. In fact, at a particular moment, only one protocol can
uniquely determine the current optimal routing to the destination. For the purpose of route selection,
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