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AC or DC?

The decision to use AC or DC power for your routers will greatly depend on the environment the routers will be deployed into. DC power is most often found in phone company central office-type (CO) environments. If your routers will be installed in a CO, you should use DC power supplies simply for the fact that in order to supply AC power in this type of environment, a power inverter must be installed to change DC to AC. Every time that electrical power is changed from one form to the other, a little power is lost. This loss of power is the main reason why a single power type is used in most sites.

If you will be installing your routers in an environment where other AC machines will be housed, it is better to use AC power supplies. The simple reason for this is consistency. All devices should use the same power type. Some people are afraid of DC power because there is no receptacle - the power feed gets wired directly to the power supply. This means that you can't simply unplug the router and move it.

Source: Cisco Router Configuration & Troubleshooting by Mark Tripod, New Riders, 1999

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This was last published in August 2000

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