[Soekris] PoE issue and alternate fix
rjw at alembic.com
Sat Oct 28 04:47:57 UTC 2006
we are installing 6 net4526's at a relay point and bought a Netgear
"ProSafe 16 Port 10/100 Switch w/PoE model FS116P". had assumed that
it would "just work" but after reading John's post did a bench test
before intalling it in the field.
the Netgear also didn't work directly with the Soekris. it would not
be our first choice to modify the 4526's as we want all the units in
the field to be interchangeable.
in looking at the Netgear FA116P it would not be compatible with John's
modification which he tested with an HP switch.
our soution involved simple jumpers on in the Netgear to supply power on
both the transformer center-taps and the "spare" pairs.
see http://wscicc.org/fs116p/ for an alternate modification and discussion
of some PoE issues.
we find that the Soekris is mostly compliant with 802.3af (save the use
of a transformer-coupled DC/DC converter to provide galvanic isolation).
but the standard permits using either "spare" pairs for power or data
pair transformer center-taps or both, and does not require powering both.
so the main issue in both the John's HP switch and our Netgear example
is the choice of the switch manufacturer to provide power on only the
compliance with the 802.3af standard does not guarantee that equipment
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