Hubs, Switches, Routers: What’s the Difference?

More on Small Business Networking

Originally posted on April 18, 2005. Updated on July 25, 2011

 I have a small business network that’s been in place for many years, and we’re finally getting around to a long overdue replacement of a dozen or so old desktop computers. The technician doing the work says that our computers are networked together using a hub and recommends that we replace it with a switch. I’m hesitant to do so, however — the hub has never given us any problems, and I’m not really clear on what benefit, if any, a switch will bring. What’s the difference between a hub and a switch (as far as I can tell, they look pretty much the same) and will going with the switch justify the effort and expense? 

 It’s true that as far as outward appearance is concerned, hubs and switches appear very much alike. Both also serve the same basic function — to provide a centralized connection for your PCs and other network equipment. But under the hood, hubs and switches operate quite differently, and replacing the hub with the switch is definitely worthwhile.

Why? A network hub is essentially a “dumb” device that has no knowledge of what devices are plugged into it, where data is coming from or where it’s going. Therefore, when Computer A sends data to Computer B through a hub, the hub simply retransmits, or “repeats”, the data to each and every port in a process called a “broadcast.” Each device connected to the hub then checks to see if the data — known as a frame — is addressed to it in order to determine whether to accept or ignore it.

The problem is that the hub’s “send everything to everyone” approach is that it generates lots of unnecessary network traffic, which in turn causes network congestion and seriously limits performance. Since all devices connected to a hub must take turns sending or receiving data, they spend lots of time waiting for network access or retransmitting data that was stepped on by another transmission (this is what a hub’s “Collision” light indicates).  

By contrast, a network switch is an intelligent device that can actively manage the data going through it. Unlike a hub, a switch knows which computers are connected to each of its ports — it identifies them by their MAC address— as well as the source and destination address of each data frame in encounters.

When Computer A sends data to Computer B over a switch, the switch sends only the data to the port Computer B is connected to. This limits unnecessary traffic, provides better performance, and leaves other devices connected to the switch free to simultaneously communicate via their respective ports.  So even while Computer A and B are exchanging data, Computer C and Computer D (and E and F, and so on) can still transmit and receive data.

In addition, while a hub is a shared-bandwidth device — it provides 10 or 100 Mbps of total data throughput that’s shared among all of its ports — each port on a switch gets 10 or 100 Mbps of dedicated bandwidth.

Years ago, switches were considerably more expensive than hubs, so the hub was commonly used in situations where cost was as important a consideration (or more so) as performance. These days, however, switches have become quite inexpensive — a basic 16 port 10/100 Mbps switch can be had for as little as $60. While faster Gigabit(1,000 Mbps) switches and those that provide more advanced features such as data prioritization or network management do cost more, they’re still relatively inexpensive.

As for the effort to install a switch, it’s minimal. Just unplug your devices from the hub, plug them into the switch, and you’re pretty much done.

In a nutshell, if you want to get the most out of your new computers, this is an excellent time to kick that hub to the curb and replace it with a shiny new switch.    

Adapted from PracticallyNetworked.com, part of the EarthWeb.com Network.