The following information will help explain why different sized networks need specific routing types as they have different network requirements. Let me start off by giving you a summary of the choices we have available to use, which are static, default, and dynamic routing.
Static Routing is when the administrator manually adds routes to the routing table of a router. This method is not suitable for large networks however it makes routing table maintenance in smaller networks easier, especially if no network growth is in sight.
Default Routing is where routers are configured to send packets towards a single router. This is great for small networks or networks with a single entry and exit point. It is not commonly used.
Dynamic Routing automatically propagates routing information. This is the most widely used method. It is also the most complicated method of routing. Some advantages of dynamic routing include its ability to handle large networks and that it automatically adapts topology to reroute network traffic if needed.
Small offices, for example; that are connected to an ISP via a single router, would require Static Routing; especially if it does not expect to grow at all in the coming years and due to its small size. This type of routing is easy to use and manage and costs significantly less than Dynamic Routing.
Larger office buildings, for example; with multiple interconnecting routers within the building would be better suited with Dynamic Routing due to the network’s large size and the number of routers that are involved. Dynamic Routing is great for businesses who expect fast growth as it has automatic rerouting capabilities.
If you decide to use Dynamic Routing, there are 3 different routing protocols you can use which have their advantages and disadvantages that depend on the size and type of network it requires.
Routing Information Protocol (RIP) is a standardized vector distance routing protocol that uses hop counts as its metric. It is commonly used for routing Internet traffic and is an interior gateway protocol. One of the main advantages of RIP is that it is simple to configure and implement however cannot scale to large networks and only has a hop count of 15. RIP also has a high recovery time when network topology changes.
Enhanced Interior Gateway Routing Protocol (EIGRP) is a routing protocol created by Cisco and is based on the concept of Interior Gateway Protocol (IGRP). It is a sophisticated distance vector routing protocol that includes optimizations to reduce routing instability due to topology changes, bandwidth usage, and processing power. EIGRP collects information and is stored in 3 tables. It also does not rely on periodic route dumps. EIGRP was designed for Cisco devices initially however in 2013, EIGRP was made open standard. EIGRP has a max hop count of 255 and default of 100 and has a Hello timer of 5 seconds and a dead time of 15 seconds.
Open Shortest Path First (OSPF) is a dynamic routing protocol. It is intended for IP networks and is a link state routing protocol and is usually assembled with interior gateway protocols. It is one of the most widely used interior gateway protocols for large enterprise networks. OSPF routes packets using a single router domain and then create a topology map. OSPF is an open protocol. OSPF has an unlimited hop count. It also has a Hello timer of 10 seconds and a dead time of 40 seconds.
When determining which routing protocol is better for the given situation, there are many areas that affect this decision however it comes down to the architecture and policies of the company. First, if you are using any router besides Cisco’s, you should go with EIGRP as it is easy to configure, fast, and reliable. EIGRP is also great for larger networks as the maximum hop count is 255 and has excellent expansion capabilities. If the network is on the smaller side, you could go with RIP as it has a max hop count of 15. Finally, if the network is extensive and needs to be vendor independent as well as supported by all vendors, OSFP would be ideal.