Dynamic routing protocols have evolved over several years to meet the demands of changing network requirements. Although many organisations have migrated to more recent routing protocols such as Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF), many of the earlier routing protocols, such as Routing Information Protocol (RIP), are still in use today.
One of the earliest routing protocols was RIP. RIP has evolved into a newer version: RIPv2. However, the newer version of RIP still does not scale to larger network implementations.
To address the needs of larger networks, two advanced routing protocols were developed:
OSPF and Intermediate System–to–Intermediate System (IS-IS). Cisco developed Interior Gateway Routing Protocol (IGRP) and Enhanced IGRP (EIGRP). EIGRP also scales well in larger network implementations.
Additionally, there was the need to interconnect different internetworks and provide routing among them. Border Gateway Protocol (BGP) is now used between Internet service providers (ISP) as well as between ISPs and their larger private clients to exchange routing information.
As you have seen earlier in the IPv6 section, the advent of numerous consumer devices using IP addresses, the IPv4 addressing space is nearly exhausted . Thus IPv6 has emerged. To support the communication based on IPv6, newer versions of the IP routing protocols have been developed
Routing protocols are used to facilitate the exchange of routing information between routers. Routing protocols allow routers to dynamically learn information about remote networks and automatically add this information to their own routing tables
Routing protocols determine the best path to each network, which is then added to the routing table. One of the primary benefits of using a dynamic routing protocol is that routers exchange routing information whenever there is a topology change. This exchange allows routers to automatically learn about new networks and also to find alternate paths if there is a link failure to a current network.
Compared to static routing, dynamic routing protocols require less administrative overhead.
However, the expense of using dynamic routing protocols is dedicating part of a router’s resources for protocol operation, including CPU time and network link bandwidth. Despite the benefits of dynamic routing, static routing still has its place. There are times when static routing is more appropriate and other times when dynamic routing is the better choice. More often than not, you will find a combination of both types of routing in any network that has a moderate level of complexity. You will learn about the advantages and disadvantages of static and dynamic routing later in this section.