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I have a PoE+ switch (ZyXEL GS1100-8HP) that has a button on the front to toggle IEEE 802.3az compliance. I looked this up and found that it was a power management specification known as "Energy-Efficient Ethernet".

From the Wikipedia page, it seems that the primary effect is that the transmit path of the physical layer is put to sleep when idle. The user manual for the device says about the same thing.

Granted that for home use (the Wikipedia page mentions this and also it seems logical) savings are probably minimal. Also, at pretty much any given time something on my network is sending something -- a quick glance at Wireshark shows a typical stream of whatever; ARP, Dropbox stuff, SSDP, etc. and the activity lights on my switches confirm.

That said, I don't know why I would disable it. Without knowing more about it it seems benefits will be either zero or positive, i.e. it can't hurt.

So my question is: Why wouldn't I want to enable 802.3az? The fact that there's a toggle button on the front of this switch means that somebody somewhere seems to know that there's a reason to disable it; what is that reason?

Jason C
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3 Answers3

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From the user guide of the product:

An EEE-enabled device initiates Low Power Idle (LPI) signals to negotiate and wake up the remote device when there is data to be transmitted. To use EEE, both devices should be EEE compliant.

EEE is configured on a per-system basis in the Switch. If one of the networking devices that connect to the Switch doesn't support EEE, EEE may not work in the Switch to save power.

Press in the IEEE 802.3az EEE ON/OFF button on the front panel to turn on the EEE feature. Disable it if you don't want the network performance to be impacted due to the latency from the additional time required for the sleep and wake transition or if the remote side doesn't support it.

This basically says that if one device connected to the switch does not support 802.3az then the power saving function might not work, hard to tell so just try it. But it does lead to a slight latency so if that is an issue then turn off the energy saving function.

ojs
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In my case [router does not support it, laptop does], the connection kept on dropping and reconnecting very quickly (within a couple of seconds). I had to disable Energy-Efficient Ethernet to get a functional connection.

Milind R
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There are some usages, that need EEE disabled. For example Dante audio networking will not work with energetically efficient switches.

Marci
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