Auto-Enabling of PoE
PoE is enabled by default and power is automatically allocated to all PoE-capable
ports on bootup. Because the
inline power configuration is applied on all PoE-capable ports by default, the PD is powered up
as soon as it is connected to the port. If the PoE power allocation must be disabled
on bootup, use the
no inline power command and the
write memory command. Upon reboot, all the saved PoE configurations are applied and PoE is not
enabled.
For a stack member or PE, the master unit sends the default
inline power configuration or non-default PoE configuration while joining the stack or SPX system.
Until then, power is not applied on the member or PE unit ports. If there is no master
unit detected after member bootup, the ports will not be enabled with power until
the master comes up.
Decoupling and Coupling of PoE with Data Link operations
Although PoE and data link operations are functionally independent of each other, some data link operations affect the operational behavior of PoE ports. To overcome this limitation, data link operation is decoupled with inline power by default. In the default state, the data link operational behavior on a PoE port does not affect the power state of the powered device (PD) that is connecting to the port.
From FastIron 08.0.70b onwards, you can override the default behavior of data link
decoupling using the
inline power couple-datalink command. This command links the behavior of PoE configuration with the
interface disable or
interface enable configuration. When the behaviors are linked, the
interface disable command also removes the power on the port (disables power when the interface is
disabled).
The following data link operations can affect the operational state of PoE on the PoE ports:
- Using the
interface disablecommand on the power sourcing equipment (PSE) port interface. - LAG operational changes can affect the PoE power state if data link coupling is enabled.
That is, power on LAG ports is impacted when the LAG is undeployed, the
interface disablecommand is issued on the LAG port, or an interface is deleted from the LAG.
In situations where data link operations tamper with PoE configurations and disable
the power on the port, the interface must be enabled so as to get the power enabled.
To reinstate the default setting of the data link decoupling, you must configure the
inline power command on the interface.
Upgrade and Downgrade Considerations
Upgrade impact: A configuration assuming the default as
no inline power will show a behavior change because all ports will get power. If you do not want
PoE on a port, the PoE must be disabled after bootup. The
decouple-datalink parameter of the
inline power command in the PoE configuration will be ignored when upgrading to FastIron 08.0.70.
Downgrade impact: After a downgrade, all PDs are powered down and you must specifically enable inline
power on the ports. There is no impact to the
decouple-datalink configuration keyword of the
inline power
command.. However, the
inline power couple-datalink command will not be recognized by the downgraded version.
ISSU Impact: If there is a change in firmware versions between FastIron images when the image upgrade is using in-service software upgrade (ISSU), there will be an increase in the time taken for the upgrade. Because there is a chance that a PD may take power from two units of the stack, ISSU must wait to reload a second unit until the firmware upgrade finishes on one unit. If the firmware upgrade is taking place on one unit, that unit will not deliver power to the PD. If another unit is reloaded at the same time, the PD loses power from both units. Only after the firmware upgrade is finished and power is stabilized on all ports can ISSU begin upgrading the image on the next unit. This consideration does not apply to PE ports, because all the PEs are reloaded together during an upgrade using ISSU.
Backward Compatibility
New PoE configuration files are not backward compatible with respect to the default
inline power and
inline power couple-datalink configurations. Other configurations of the
inline power power-limit command are backward compatible.