Although Ethernet is usually thought of as having a star topology, it’s also possible to build an Ethernet network as a ring. This configuration has the advantage of providing a redundant pathway if a link goes down. A ring topology is often used in application such as traffic signals and surveillance, where long distances may make it difficult to run fiber in a star formation from a central switch and where downtime must be minimized.

The key to the ring topology is spanning tree protocol. One switch-in this case, the switch in the central office-is the root of the spanning tree. A node on the opposite side of the ring blocks on of the ports leading back to the root switch, creating a topology that functions like a long line of Ethernet switches. If a link breaks, the network reorganizes itself to relink all the switches. Although this convergence isn’t instantaneous, it takes only a few seconds to bring the network back. In the diagram below, Hardened Managed Ethernet Switches create a ring topology that operates at Gigabit speed to support traffic cameras at the interaction. Industrial Ethernet Serial Servers make the connection from the switch to the serial interface on the traffic signals, enabling central management of the lights across the Ethernet network.

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One of the most aggravating infrastructure challenges occurs when you get asked to put a workstation in some inconvenient, too far, difficult-to-wire spot. If there’s a room at the far end of some unused hallway, or a shack at the edge of campus, chances are you’re going to get a request for an Ethernet port there.

Whenever you need to put a connection in one of these types of places, your first move should be to check to see if there’s any existing cable that can be adapted for Ethernet by using Ethernet extenders. Most modern buildings have unused voice-grade wires or unused coax. Additionally, many campuses have installed 25- or 50-pair telephone trunk cables between buildings. You can hijack these unused wires for Ethernet use.

Ethernet extenders are easy to set up—all you need to do is to plug in one at each end of the twisted-pair wire or coax. Sometimes you’ll also need to set a DIP switch for local or remote operation. Once the Ethernet extenders are installed, there’s nothing to configure, and the extenders are transparent to network operation.

Ethernet extenders can often save you the time, aggravation, and expense of pulling new cable. If you have the right cable already installed, Ethernet extenders are definitely the way to go when it comes to putting your network into out-of-the-way or distant locations. Best of all, when you pull off that difficult install, you look like a miracle worker!