What is Administrative Distance?

Administrative distance is part of a specific routing methodology for routers made by the Cisco company, a leader in networking electronics. Administrative distance has nothing to do with actual human administration or remote work. It is part of a special metric for providing the best routing paths for information.

The basic idea of routing consists of two parts. Routers and other equipment find the best paths for routing information. They then use these paths to transport “packets” of information.

The routing metric includes protocols and algorithms for finding the best routing paths. That’s where administrative distance comes in. Administrative distance is just one of several factors that are used in the Cisco routing metric.

Within the general method of routing, there are different kinds of routing strategies represented by different protocols. Some of these are “static,” or set up prior to transmission. Others that have more flexibility are known as “dynamic.” There are also host-intelligent routing protocols where routers are just passive senders, and router-intelligent protocols where the routers themselves determine the paths for the flow of information.

When routers use administrative distance, this measure of a specific path’s relevance and capacity creates something that network engineers call “believability.” A believable path is more reliable and more likely to be chosen. It will have a low administrative distance value assigned to it. Administrative distances higher than a certain threshold will often be ignored by the router.

In addition to reliability, routers and other administrative units look at bandwidth, delay, and other factors to find the best routes for information. A routing algorithm or protocol is a complex metric that provides for a kind of “artificial intelligence” that helps human network engineers to boost productivity in a network or system. That’s why beginning network professionals spend a lot of time getting their knowledge of these routing protocols up to par.

It’s important to understand that administrative distance and other similar aspects of routing are part of Cisco’s proprietary routing technology. Because Cisco is such a powerful presence in the world of IT, network engineers will often study the company’s metrics as part of a general education program. Cisco provides a lot more information on their proprietary technologies on the company’s web site.