All routing protocols have the same purpose: to learn about remote networks and to quickly adapt whenever there is a change in the topology. The method that a routing protocol uses to accomplish this depends on the algorithm it uses and the operational characteristics of that protocol. The operations of a dynamic routing protocol vary depending on the type of routing protocol and the specific operations of that routing protocol. The specific operations of RIP, EIGRP, and OSPF are covered later. In general, the operations of a dynamic routing protocol can be described as follows:
1. The router sends and receives routing messages on its interfaces.
2. The router shares routing messages and routing information with other routers that are using the same routing protocol.
3. Routers exchange routing information to learn about remote networks.
4. When a router detects a topology change, the routing protocol can advertise this change to other routers.
Before delving deeper into dynamic routing let’s think back to Static Routing. And look again at is usage, advantages and disadvantages;
Static routing has several primary uses, including the following:
■ Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly.
■ Routing to and from stub networks (see section on static routing).
■ Using a single default route, used to represent a path to any network that does not have a more specific match with another route in the routing table.
Static routing advantages are as follows:
■ Minimal CPU processing
■ Easier for administrator to understand
■ Easy to configure
Static routing disadvantages are as follows:
■ Configuration and maintenance are time-consuming.
■ Configuration is error-prone, especially in large networks.
■ Administrator intervention is required to maintain changing route information.
■ Does not scale well with growing networks; maintenance becomes cumbersome.
■ Requires complete knowledge of the entire network for proper implementation.
Now before we cover let us consider dynamic routing and its advantages and disadvantages
Dynamic routing advantages are as follows:
■ Administrator has less work in maintaining the configuration when adding or deleting networks.
■ Protocols automatically react to the topology changes.
■ Configuration is less error-prone.
■ More scalable; growing the network usually does not present a problem.
Dynamic routing disadvantages are as follows:
■ Router resources are used (CPU cycles, memory, and link bandwidth).
■ More administrator knowledge is required for configuration, verification, and troubleshooting.