Back to the Basics: Is Static or Dynamic Routing Better?

The TL;DR of this question: Neither. They're just different.

Read on to learn when to use each routing solution.

Routers are an essential piece of hardware in networks. They preserve the knowledge of the network topology and use that information to forward packets to each destination. The goal is always to use the best path across the topology, whether there are just a few or several routes available.

For routers to successfully transfer packets, they must have an updated routing table. For context, a routing table contains information only for directly connected networks and nothing else (by default). So, how can a router send data to requested destination networks if such knowledge does not exist?

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In this article, we will discuss static and dynamic routing as solutions for gaining that crucial knowledge, the advantages and disadvantages of each, as well as the recommendations for proper use. 

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The Learning Process

As previously mentioned, the routing table does not contain any information for networks that are not directly connected. However, the router can learn about this information by using either static routing when network information is manually entered, or by dynamic routing when information is dynamically learned through a routing protocol.

In the end, whatever routing method is used, both will provide sufficient knowledge for the proper routing of packets. However, using the more appropriate method in a specific scenario will provide more optimized routing.

So, how do you know which is better for your network--static or dynamic routing? To find that out, let’s take a look at what each approach offers then we can better understand their benefits and shortcomings.

Static Routing Overview

In general, static routes define explicit paths between two routers or Layer 3 devices. For a router to use static routes when sending data, an administrator must first manually configure them. Therefore, for each destination network that will be available and used in the enterprise campus, a static route must exist.

Additionally, since everything is based on manual configuration, every time there is a topology change, one or more static routes already installed in the routing table will require a manual update and an appropriate reconfiguration.

As a result, static routing allows the routing behavior to be precisely controlled and only the desired paths to each destination to be used for sending network traffic. However, the nature of static routing does not allow it to be used in every single situation, but only in certain scenarios.

When to Use Static Routing

Because this concept is completely static, it should only be used in small networks, such as branch offices, Small Office Home Office (SOHO), point-to-point links, or simple hub-and-spoke topologies. In addition, static routing should be avoided in unstable networks because it will require a manual reconfiguration of the static routes when a network change occurs.

A common use of the static routes is a default static route, which is a gateway of last resort for the routers.

Dynamic Routing Overview

The foundation of a dynamic routing protocol is an algorithm that performs various processes in the background to exchange network information through updates between the participating routers. Also, the protocol dynamically adapts to network changes when they occur.

The routing algorithm is responsible for determining the optimal path between different segments in the enterprise network and frequently updating the routing table with the latest network changes.

The best part about using a dynamic routing protocol is that the administrator just has to enable it on the routers and, from that point on, it automatically starts learning routes and makes appropriate updates when needed.

When to Use Dynamic Routing

The most common scenario for using a dynamic routing protocol would be in a large environment such as an enterprise campus, an unstable network that frequently changes, and a network where applications heavily depend on uninterrupted network connectivity or at least short convergence.

Several interior routing protocols can be used inside the enterprise network, such as OSPF, EIGRP, RIP, and IS-IS. Whichever one is used in the network will depend on many different factors, but all of them will fulfill the main task, and that is learning about the enterprise segments and providing full network connectivity.

Use Static Routing in Smaller Networks

One of the advantages of using static routing is that it does not consume a lot of resources such as network bandwidth and CPU processing on the routers. This is because you create only those static routes that you will need, and this is all that these routers will use.

When the static route fails, reconfiguration is a must. Consequently, this leads to a delay and period of network inactivity, until the administrator implements the necessary configuration changes. Keep in mind that backup static routes can also be configured, but this will make things even more complicated since the number of routes will drastically increase.

For a small network with up to three routers, static routing is the preferable solution. This is also true of point-to-point or hub-and-spoke topology where static routing is the appropriate strategy. The configuration is extremely simple, and you choose the paths that packets will take when sending information to any destination. 

Use Dynamic Routing in Larger, More Complex Networks

With dynamic routing, the router learns all possible routes for a single destination from the neighbors and keeps them in the routing protocol database. As a result, this consumes extra memory, but at the same time, it provides an extra benefit. This benefit is that the router knows what to do next in every situation when an active route in the routing table stops working. 

Dynamic routing protocols decide on their own which routes are best according to the algorithm and metrics used and apply those in the routing table.

 In larger environments consisting of many routers and a lot of stub networks, the static routing would be the wrong approach. You would need to create static routes for each segment, and this must be done on each router.

This is very time-consuming and will most likely result in an undesired misconfiguration. Therefore, using a dynamic routing protocol in a large network would be a better fit. It will dynamically provide network knowledge, quickly adapt to network changes, and converge fast when necessary.

And the Better Fit for My Network Is…

Once you know about the topology of your network, the application requirements, or possible future expansion plans, only then do you select static or dynamic routing. In the end, whichever routing option is selected, it must provide sufficient routing knowledge to all routers, so you will have full network connectivity.

Ready to Configure Your Routers?

Now that you have determined which routing protocol is better for your network, you will want to look at how to put either of these into action through the following articles. Here are some resources you might find helpful.

• Interior Routing Protocols Comparison: RIP, EIGRP, OSPF, IS-IS
• A Quick Guide to EIGRP Configuration with Stub Routing

Click here to see all our resources around static and dynamic routing, their configuration guides, and troubleshooting guides.