Article ID: 11385
Products
Matrix N-Series DFE
SecureStack C3, C2, B3, B2, A2
D-Series
G-Series
Changes
Attached an IP Phone (for example, Siemens Optipoint 4000) to a "
"-suffixed unit of one of the above-stated product lines, using an 8-conductor UTP cable.
Symptoms
The host unit's Power over Ethernet (PoE) is not powering up the phone, though both devices support PowerDsine pre-802.3af-standard power detection.
Cause
The IP Phone PoE client is one example of a pre-802.3af-standard device which uses the spare pairs (4-5 / 7-8) for power.
The above-stated Enterasys products use the data pairs (1-2 / 3-6) to supply power, as do most modern-day switches.
The 802.3af standard states that the device receiving power should be able to receive power using either method. The IP Phone doesn't support this as it is pre-standard.
The Enterasys products do have a PoE detection mode capability (default = '
code:set inlinepower detectionmode auto
') to accommodate both the 802.3af-standard "Resistive" method and the pre-standard "Capacitive" method (
9872). But since this has nothing to do with which pairs are used to provide power, it will not correct the described incompatibility.
Solution/Workaround
Functions as Designed (FAD).
Workaround: Use a pre-standard mid-span PoE source, or an external power supply, for the IP Phone.
