Page 270 -

Appendix A
Green IT Checklist and Recommendations 235

required. If some switches have a few active ports and others have
unused ports, consolidate connections and unplug one of the
switches.
■ Replace old, inefficient network hardware. Concerns about network
energy consumption have led manufacturers to design higher-efficiency
power supplies. Newer equipment consumes less power while delivering
the same or improved function. Use the local cost of power to evaluate
each potential replacement to calculate the payoff period.
■ Consolidate multiple small switches, which might have been pur-
chased as the network grew, into a single larger switch. A single
high-port-count switch is more energy efficient than many smaller
switches.
■ Calculate actual power requirements in switches with modular
power supplies. Switches might have been over-provisioned when first
installed, because power consumption was not a major consideration in
the past. Power supplies operate more efficiently at a higher percentage
utilization of available capacity. An unneeded supply increases available
capacity, so at a given level of utilization, percentage utilization is lower, ptg
resulting in reduced efficiency. Put another way, using 40 watts of a 50-
watt supply is much more efficient than using 40 watts of a 100-watt
supply. If possible, remove one or more of the supplies. If the additional
supply was put in place to provide redundancy, however, removing it
might not be an option.
■ Review use of stand-alone virtual private networks (VPNs), fire-
walls, and DHCP servers. These stand-alone appliances have prolifer-
ated, and each contains a power supply, takes up rack space, and produces
heat. Moving these functions into a modular switch can reduce power and
heat.
■ Determine whether 100Mbps is sufficient for workstation users.
Most new workstations come with 1Gbps Ethernet ports, which consume
roughly 2 watts more than 100Mbps. Configuring 1Gbps on the work-
station and on the corresponding switch port adds 4 watts to each work-
station. Although not significant for a small- or medium-sized site, the
unnecessary power use and heat can add up for a large site.
■ Evaluate use of Power over Ethernet (PoE). It is an efficient way to
power IP phones, wireless access points, and security cameras. It is not
necessary on all switch ports, however, because it cannot be used to power
workstations or servers. If PoE is available on all switch ports, make sure