Auto enabling of PoE

PoE is enabled by default and power is automatically allocated to all PoE-capable ports on bootup. As the 'inline power' configuration is applied on all PoE-capable ports by default, PD is powered up as soon as it is connected to the port. If the PoE power allocation needs to be disabled on bootup, use the no inline power command and do write memory. Upon reboot, all the saved PoE configurations would get applied and PoE will not be enabled.

For a stack member or PE, 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 master comes up.

Decoupling and coupling of PoE with datalink operations

Although PoE and datalink operations are functionally independent of each other, some datalink 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 datalink operational behavior on a PoE port does not affect the power state of the powered device (PD) that is connecting to the port.

From 08.0.70b release onwards, user can override the default behavior of datalink decoupling using the inline power couple-datalink command. This command links the behavior of PoE configuration with interface disable or interface enable configuration. When they are linked, the interface disable command also removes the power on the port (disables power when interface is disabled).

The following are some datalink operations that can affect the operational state of the PoE on PoE ports:
  • Using the disable command on the power sourcing equipment (PSE) port interface.
  • LAG operational changes can affect the PoE power state if datalink coupling is enabled. That is power on LAG ports are impacted when LAG is undeployed, when the disable command is issued on LAG port, or when an interface is deleted from the LAG.
In situations where datalink operations tamper with PoE configurations and disable the power on the port, the interface has to be enabled so as to get the power enabled. To reinstate the default setting of datalink decouple, user must configure the inline power command on the interface.
The no function of the inline power couple-datalink command does not restore the default setting but only disables the power on the port.

Upgrade and downgrade considerations

Upgrade impact: A configuration assuming default as no inline power will have a behavior change, as all ports will get powered. So if a user does not want PoE on a port, it has to be disabled after boot. The decouple-datalink keyword in the PoE configuration will be ignored upon upgrade to 08.0.70 release.

Downgrade impact: After a downgrade, all PDs will be powered down and the user has to specifically enable inline power on the ports. No impact for the decouple-datalink configuration keyword. However, the inline power couple-datalink command will not be recognized by the downgraded version.

ISSU Impact: If there is change in firmware version between FastIron images where image upgrade is happening with ISSU feature, there will be increase in time taken for upgrade. Because, there is a chance that a PD might be taking power from two units of the stack, it requires the ISSU to wait to reload another unit until firmware upgrade finishes on one unit. If firmware upgrade is happening on one unit, that unit will not be delivering power to the PD and during this time if another unit is reloaded, PD loses power from both the units. So, only after firmware upgrade is finished and power is stabilized on all the ports, ISSU can start upgrading the image on the next unit. This consideration is not applicable for PE ports as all the PEs are reloaded together for ISSU upgrade.

Backward compatibility

New PoE configuration file is not backward compatible with respect to the default inline power and inline power couple-datalink configurations. Other configurations of inline power power-limit command are backward compatible.