One of the things I found to be useful at Cisco Live is EnergyWise. What’s EnergyWise? Simply put, it’s a protocol that allows you to see how much power everything attached to the network is consuming, as well as influence that power consumption. In this article I’ll describe how to do some simple checks and modifications using EnergyWise. Note that this is without any management software and thus only half the solution: together with (mostly third-party) management software, a lot of automation is possible, such as scheduled standby of devices, detailed graphs about power usage, and real-time queries.

First thing about EnergyWise configuration: it lets switches act as an EnergyWise cluster, with one master switch that gathers all data. This is a good thing really: while you can read out EnergyWise data on switches with SNMP, it’s a lengthy process, and querying one master switch makes it a lot more responsive. EnergyWise is activated by configuring cluster parameters:

energywise domain domain security shared-secret secret protocol udp port 43440 interface interface

The domain name obviously needs to be the same for all switches in one domain, just as the shared secret. Protocol currently only supports UDP but it was added to allow for future expansion if needed. Default port number is 43440, and interface is the interface on which the switches will communicate as a cluster (most likely management interface). Yes, even if you just have one switch, this is mandatory.

EnergyWise defines 10 levels of device operation, where zero is powered off and 10 is full power. If the device is EnergyWise aware, it can use those energy levels advertised by the network to adjust its power consumption. Theoretically, a printer can go to standby, full power, turn itself off, and so on. But back to reality: without any EnergyWise aware software and devices, it’s limited to basics. But that’s enough, as you can influence PoE consumption on a port. Energy levels 1 to 10 mean PoE is allowed on a port, energy level 0 mean no PoE. So configuring a port with EnergyWise level 0 will disable PoE on that port.

Okay, interesting, but what makes this better than ‘power inline never’? Well: EnergyWise can be combined with time ranges. And that’s where it gets fun. Say I want to have all IP Phones in an office only powered up during business hours, being 8 am to 6 pm. First, make time ranges in the IOS:

time-range TIR-Work
periodic weekdays 7:55 to 17:59

time-range TIR-Free
periodic weekend 0:00 to 23:59
periodic weekdays 0:00 to 7:54

Because the IP Phones need some time to boot, start time for activity (business hours) is set to 7:55 am. Next, on the interfaces where IP Phones are attached, the following two commands do the magic:

energywise level 0 recurrence importance 100 time-range TIR-Free
energywise level 10 recurrence importance 100 time-range TIR-Work

Now, automatically every day, the IP Phones boot up, and after business hours, they power down, saving energy. You need both time ranges, as EnergyWise will stay in the state it was changed last to otherwise. This is a very simple setup, and more fine tuning is possible, including the ability to only power down if there is no more activity on the IP Phone.

While this is not something widely deployed yet, I hope people will see the potential.

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