Considering Routing Protocols

Considering Routing Protocols
in Network Design
In the previous section, you learned how to allocate IP addresses to allow for aggregation
through summarization. In this section, we will discuss the different routing protocols and how
they can be configured to meet the network design requirements. When designing a network,
one routing protocol can meet certain requirements, while another one cannot. These requirements
usually include one or more of the following:

Summarize network route advertisements.

Support a large number of devices within a network.

Offer speedy convergence to promote network stability.

Use a hierarchical network design.
There are many routing protocols available, but to facilitate the summarization requirement,
the protocol needs to be a classless routing protocol. This means that it must send the subnet mask
in its routing updates. Supporting a large number of devices and offering speedy convergence can
be seen as mutually exclusive, but some protocols have features to make both possible.
Other routing protocols such as Routing Information Protocol version 1 (RIPv1) and Interior
Gateway Routing Protocol (IGRP) are classful, so they do not support these requirements.
RIP version 2 (RIPv2) is a classless routing protocol but does not scale in a large network
because of slow convergence. Because of these limitations, we will look at
Open Shortest Path
First (OSPF)
,
Enhanced Interior Gateway Routing Protocol (EIGRP)
,
Integrated Intermediate
System to Intermediate System (IS-IS)
, and
Border Gateway Protocol (BGP)
,
in that order.