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Reminder. Priorit y disconnect examples are appl icable only when t here is
inadequat e power remaining t o power an incoming device.
When a PD is being connect ed t o a port wit h a higher priorit y level t han all ot her in t he slot , t he
incoming PD will aut omat ically be grant ed power over t he ot her devices, regardless of it s physical port
number.
In order t o avoid a power budget def icit , anot her port in t he slot is disconnect ed. In det ermining which
port t o power of f , t he syst em sof t ware f irst select s t he port wit h t he lowest conf igured priorit y level.
For exampl e, if a crit ical priorit y device is being added t o a slot in which f ive exist ing devices are
at t ached t o high priorit y and one device is at t ached t o a low priorit y port , t he low priorit y port is
aut omat ically disconnect ed, regardless of it s physical port number.
If all exist ing devices are at t ached t o wit h t he same lower priori t y level , t he syst em sof t ware
disconnect s t he port wit h bot h t he lowest priorit y level. For example, if a crit ical priorit y device is being
added t o a slot in which six exist ing devices are at t ached at high priorit y, t he high priorit y port wit h t he
highest physical port number is aut omat ically disconnect ed.
Priority Disconnect is Enabled; Incoming PD Port has Lowest Priority Level
Reminder. Priorit y disconnect examples are appl icable only when t here is
inadequat e power remaining t o power an incoming device.
When a PD is being connect ed t o a port wit h a lower priorit y level t han all ot her in t he slot , t he
incoming PD will be denied power, regardless of it s physical port number. Devices connect ed t o ot her
higher-priorit y will cont inue operat ing wit hout int errupt ion.
Priority Disconnect is Disabled
Reminder. Priorit y disconnect examples are appl icable only when t here is
inadequat e power remaining t o power an incoming device.
When priorit y disconnect is disabled, power will be denied t o any incoming PD, regardless of it s port
priorit y st at us (i. e. , low, high, and crit ical) or physical port number.
Understanding Guard Band
Guard Band f unct ionalit y is implement ed when t he swit ch has t o provide power t o a newly connect ed
PD. This f unct ionalit y is more relevant on swit ches t hat have a lower amount of t ot al PoE power
available f or t he swit ch but a higher def ault maximum PoE power available t o some port s.
•
If t he amount of power remaining is less t han t he port 's conf igured maximum PoE power value or t he
PD's class maximum power t hen t he swit ch will not power up t he PD.
•
This applies even if t he newly connect ed PD act ual ly requires less t han t he maximum power avail -
able f or t he port .
For exampl e, assume t he f ollowing:
•
There is 50W of PoE power remaining on t he swit ch.
•
A newly connect ed PD only requires 4W of power.
OmniSwit ch 6865 Hardware Users Guide
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