Five top tips:

  • Refresh your equipment

Cisco estimates that its new equipment gains 15% to 20% in energy efficiency every two to three years. The energy savings alone aren't enough to justify replacement, but it's a good reason to keep your refreshes on schedule.

  • Make use of energy-efficient features

These features can vary by vendor, or even by model, so check before you buy. For example, Cisco's Nexus 7000 switch can reduce power consumption in empty line-card slots, but that feature is not yet available in the vendor's more popular Catalyst 6500 series. Other vendors, such as HP, allow you to turn off empty slots, but the process is a manual one. Juniper Networks lets administrators cut power to unused ports, but only by writing a script that lowers the power once a certain activity threshold is reached.

  • Virtualise

Server virtualisation
increases network utilization and reduces network equipment needs by allowing multiple virtual servers to share one or more network adapters within the confines of a single physical server. On the switch side, features such as Cisco's Virtual Switching System allow one switch to function like many, which means more than one server can connect to the same port. This works because most organizations overprovision switching capacity based on peak loads. Reducing the total number of physical ports required lowers overall power consumption. Similarly, HP's Virtual Connect technology abstracts HP server blades from Ethernet and Fibre Channel networks. It requires fewer network interface cards, reduces cabling requirements and increases network utilization.

  • Be careful with cabinets

Make sure networking equipment that goes into a hot aisle/cold aisle row uses front-to-back airflow, not side-to-side cooling. Vendors prefer side-to-side venting, which allows them to get more equipment into the rack, but units using a side-to-side design may blow hot air back into the cold aisle, or directly into an adjacent rack, and overheat it. If the vendor doesn't offer switching equipment that supports front-to-back airflows, you'll need to retrofit the cabinet with a conversion kit, available from vendors such as Panduit and Chatsworth, which redirects it for use in a hot aisle/cold aisle configuration.

  • Use a structured network design

Your best bet for the greatest energy efficiency is to follow the Telecommunications Industry Association's TIA-942 Telecom Infrastructure Standard for Data Centres, says Rockwell Bonecutter, global lead of Accenture's green IT practice. The specification locates networking equipment in a main distribution area, which ultimately connects to servers, storage and other IT equipment in individual racks.