Dell Force10 E300, Configuration Manual

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790 | Power over Ethernet
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power-inline priority
, it breaks the tie using the third parameter, the LLDP-MED Priority advertised by the
PD, which like
power-inline priority
could be “Critical,” “High,” or “Low”. After this, if FTOS still finds a
tie, priority is based on the fourth parameter which is the ports position in the chassis; there cannot be a tie
based on this parameter.
This sorted list is dynamically updated by FTOS when:
• a user changes the
power-inline
mode or priority
• the PD advertises a different LLDP-MED priority
• the PD is connected or disconnected
FTOS always uses this sorted list of ports for allocation. When an additional PSU is added, additional ports
are powered based on this list, and PSU is removed, this same list is used to remove power from the lowest
priority ports.
power-inline mode
FTOS allows ports to be configured in one of two modes:
auto
and
static
.
auto
: Ports configured for auto mode manage the power allocation by themselves. There is no prior
reservation of power made on these ports. When no PD is connected on this port, the power allocated is
zero. Once a PD is connected, FTOS detects its PoE class dynamically and the maximum power for its
class is allocated to the port. The PD then boots using this allocated power. After bootup, if the PD is
LLDP-MED capable, it might send in Extended Power via MDI TLV to the system. In this case, the Dell
Force10 switch revises the power allocation to the value that the PD requests via LLDP-MED. The
advertised Power Requirement from the PD could be less than or greater than the currently allocated value.
Ports configured for auto mode with the
max_milliwatts
option allocate power the same way, but the
allocation never exceeds the specified maximum. If
max_milliwatts
is greater than the PoE class maximum
the system allocates only the class maximum. Note that if a PD has class maximum that is greater than
max_milliwatts
, the system allocates no power, and the PD does not power up.
static
: Ports configured in static mode reserve a fixed power allocation whether a device is connected or
not. By default 15.4W is allocated, but this is user-configurable with the
max_milliwatts
option. No dynamic
PoE class detection is performed on static ports, and Extended Power via MDI TLVs have no effect.
Extended Power-via-MDI TLV
The PD sends three pieces of information in the LLDP-MED Extended Power-via-MDI TLV:
1. Power Requirement: FTOS honors this and uses it for power allocation.
2. Power Priority—Critical, High, or Low: FTOS honors this information and uses it for power priority
calculation.
3. External Power Source: FTOS does not use this information.