Dynamic routing protocols

Static routes work well in small, stable networks. They are easy to configure and require fewer system resources. However, in networks where topology changes occur frequently, a typical practice is to configure a dynamic routing protocol. Compared with static routing, a dynamic routing protocol is complicated to configure, requires more routers resources, and consumes more network resources.

Dynamic routing protocols dynamically collect and report reachability information to adapt to topology changes. They are suitable for large networks.

Dynamic routing protocols can be classified by different criteria, as shown in Table 2.

Table 2: Categories of dynamic routing protocols

Criterion	Categories
Operation scope	IGPs—Work within an AS. Examples include RIP, OSPF, and IS-IS. EGPs—Work between ASs. The most popular EGP is BGP.
Routing algorithm	Distance-vector protocols—Examples include RIP and BGP. BGP is also considered a path-vector protocol. Link-state protocols—Examples include OSPF and IS-IS.
Destination address type	Unicast routing protocols—Examples include RIP, OSPF, BGP, and IS-IS. Multicast routing protocols—Examples include PIM-SM and PIM-DM.
IP version	IPv4 routing protocols—Examples include RIP, OSPF, BGP, and IS-IS. IPv6 routing protocols—Examples include RIPng, OSPFv3, IPv6 BGP, and IPv6 IS-IS.

An AS refers to a group of routers that use the same routing policy and work under the same administration.

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