Power Class
According to the IEEE 802.3at standard, a power class determines the amount of power a PD receives from power-sourcing equipment. When a valid PD is detected, the RUCKUS PoE device performs power classification by inducing a specific voltage and measuring the current consumption of the PD. Depending on the measured current, the appropriate class is assigned to the PD. PDs that do not support classification are assigned a class of 0.
In the IEEE 802.3af standard, the maximum power output of a port is limited to 15.4W. But some power will get lost on the Ethernet cable and therefore, the minimum power available at the PD is 13W per port.
The IEEE 802.3at standard is backward compatible with IEEE 802.3af. This standard provides up to 30W of power on each port of the power equipment. The minimum output power on each port at the PD after the cable loss is 25.5W.
The new IEEE 802.3bt standard introduced two more types of powering standards, Type 3 and Type 4, and four new classes, from Class 5 to Class 8. Type 3 can carry up to 60W for each PoE port and Type 4 can provide maximum power output of 90W per PoE port. IEEE 802.3bt is backward compatible with 802.3af and 802.3at.
The following table shows the different power classes and their respective power consumption needs.
Power Classes for PDs
Power management is enhanced to enable the port and also power up the legacy PD or Class 1, Class 2, or Class 3 PDs even if the available power is less than 30W. In releases prior to FastIron 08.0.70, the default power reservation of 30W places the ports in the denied state when the available power is less than 30W. The port remains in the denied state even if you want to use lower-class PDs on the ports. With the new enhancement, the device monitors the denied ports every 5 seconds and at every instance, if the available power is less than 30W but has more than Class 1, 2, or 3 power, the ports are enabled and, if the PD is detected in these classes, the PD is powered up. This process continues until all denied ports are monitored for PD detection or the available power is less than 4W. The PDs will not be powered up if the available power is less than Class 1 PD power (4W).
Power Requirement for Ports and PD Detection
| Available System Power | Power Reservation for PD Detection |
|---|---|
| Class 8 Power | 90W |
| > Class 7 Power (between 75W and 90W) | 75W |
| > Class 6 Power (between 60W and 75W) | 60W |
| > Class 5 Power (between 45W and 60W) | 45W |
| > Class 4 Power (between 30W and 45W) | 30W |
| > Class 3 Power (between 15.4W and 30W) | 15.4W |
| > Class 2 Power (between 7W and 15.4W) | 7W |
| > Class 1 Power (between 4W and 7W) | 4W |
| < Class 1 Power (between 0W and 4W) | Ports will be in disabled state (power-denied state) |
The PSU AC input (110-240V) remains the same while configuring perpetual PoE and fast boot PoE. Moving the PSU AC input from 240V to 110V reduces the power supply capacity. If perpetual PoE or fast boot PoE is applied on all ports, and the connected PDs are already using more than the capacity of the PSU with 110V, then there is a possibility of PSU shutdown.
ICX 7550 Models Using AC < 180V
| Model | PSU Count | Maximum 12V Output Power (W) | Maximum PoE Output Power (W) |
|---|---|---|---|
| ICX 7550-24P | 1 | 154W | 812W |
| 2 | 154W each | 812W x 2 | |
| ICX 7550-48P | 1 | 164W | 812W |
| 2 | 164W each | 812W x 2 | |
| ICX 7550-24ZP | 1 | 197W | 815W |
| 2 | 197W each | 815W x 2 | |
| ICX 7550-48ZP | 1 | 250W | 763W |
| 2 | 250W each | 763W x 2 |
Scaling numbers depend on the PSUs and the power budget of the PDs.
Maximum Number of Ports Supported for the ICX 7550
| Model | VAC (V) | PSU | Max PoE Output Power Draw (W) | Maximum Number of Ports Supported | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 802.3af/at/bt Class 3 | 802.3at/bt Class 4 | PoE Overdrive | 802.3bt Class 5 | 802.3bt Class 6 | 802.3bt Class 7 | 802.3bt Class 8 | 802.3bt Class 9 | ||||
| 2-Pair | 2-Pair | 2-Pair | 4-Pair | 4-Pair | 4-Pair | 4-Pair | 4-Pair | ||||
| 15.4W | 30W | 45W | 45W | 60W | 70W | 90W | 95W | ||||
| ICX7550-24P | 100-180 | 1 | 812 | 24 | 24 | 18 | N/A | N/A | N/A | N/A | N/A |
| 2 | 1624 | 24 | 24 | 24 | N/A | N/A | N/A | N/A | N/A | ||
| 181-240 | 1 | 950 | 24 | 24 | 21 | N/A | N/A | N/A | N/A | N/A | |
| 2 | 1900 | 24 | 24 | 24 | N/A | N/A | N/A | N/A | N/A | ||
| ICX7550-48P | 100-180 | 1 | 812 | 48 | 27 | 18 | N/A | N/A | N/A | N/A | N/A |
| 2 | 1624 | 48 | 48 | 36 | N/A | N/A | N/A | N/A | N/A | ||
| 181-240 | 1 | 950 | 48 | 31 | 21 | N/A | N/A | N/A | N/A | N/A | |
| 2 | 1900 | 48 | 48 | 42 | N/A | N/A | N/A | N/A | N/A | ||
| ICX7550-24ZP | 100-180 | 1 | 815 | 24 | 24 | 18 | 18 | 13 | 10 | 9 | 8 |
| 2 | 1630 | 24 | 24 | 24 | 24 | 24 | 21 | 18 | 17 | ||
| 181-240 | 1 | 954 | 24 | 24 | 21 | 21 | 15 | 12 | 10 | 10 | |
| 2 | 1908 | 24 | 24 | 24 | 24 | 24 | 24 | 21 | 20 | ||
| ICX7550-48ZP | 100-180 | 1 | 753 | 48 | 25 | 16 | 16 | 12 | 10 | 8 | 8 |
| 2 | 1526 | 48 | 48 | 33 | 33 | 25 | 20 | 16 | 16 | ||
| 181-240 | 1 | 929 | 48 | 30 | 20 | 20 | 15 | 12 | 10 | 9 | |
| 2 | 1858 | 48 | 48 | 41 | 41 | 30 | 24 | 20 | 19 | ||
PoE Overdrive
PoE overdrive is not part of the IEEE standard, but a RUCKUS proprietary enhancement. In releases prior to FastIron 08.0.61, a PD could negotiate only for a power lower than the limit defined by the power class of the PD through the LLDP-MED messages. Beginning with FastIron 08.0.61, PoE overdrive allows the Class 0 and Class 4 PDs to negotiate for power greater than the 30W allocation (refer to PoE Overdrive Limit on Different Hardware Models through PDs Allowed for POE Overdrive on PoE+ Ports for PoE overdrive support details). The maximum power that can be processed based on LLDP-MED negotiation is limited to the hardware capability of the PSE. If the PD negotiates for power more than the hardware limit, the PSE allocates only up to the hardware capability of the PSE.
PoE overdrive is disabled by default.
When RUCKUS PDs negotiate for power greater than the 30W allocation on PoE+ ports
that support overdrive through LLDP-MED messages, PoE overdrive is enabled
automatically. When the port mode dynamically changes to overdrive mode, the power
is cycled (off and on) on the port. To avoid PD reload, manually apply the inline power overdrive
configuration on the port before connecting the PD. PoE overdrive is a per-port
configuration and can be configured on a range of ports.
If PoE overdrive is enabled on the ports dynamically (when overdrive-supported RUCKUS PDs are connected), it is disabled on the ports automatically when the PD is disconnected. This automatic overdrive configuration is not displayed in the running configuration.
By default, the initial power allocation is 60W on PoH ports and 30W on PoE+ ports. With the PoE overdrive configuration, the initial power allocation is 95W on PoH ports and 30W on PoE+ ports.
The ICX devices listed in Ports Supporting Overdrive Feature are a mix of 2-pair and 4-pair ports that support the 802.3bt standard. Automatic overdrive is used for 2-pair ports and only RUCKUS-tested third-party PDs receive more than 30W. RUCKUS PDs that require more than 30W on 2-pair ports automatically get the power without any configuration, and there is no reload of the PD.
inline power overdrive
command on the 2-pair ports only. The ICX devices with 4-pair ports listed in Ports Supporting Overdrive
Feature require the inline power overdrive
command to supply more power to PoH and PoE++ PDs.
You must manually configure the inline power
power-limit command on the port to support PoH and PoE++ PDs. The ICX
devices listed in PoE Overdrive Limit on
Different Hardware Models supply more power to PoH and PoE++ PDs by configuring the
inline power
overdrive command. The PoH and PoE++ PDs get power and come under
Class 5 to Class 8 as classified under the 802.3bt standard. The power-supplying
devices for the ICX devices listed in PoE Overdrive Limit on
Different Hardware Models provide only 802.3bt standard power, irrespective of whether the
connected PD is 802.3bt or LT PoE++-compliant.
The PoE overdrive allocation varies depending on the hardware models, as shown in the following table.
PoE Overdrive Limit on Different Hardware Models
PoE Overdrive Limit for ICX 7550
| Classes | Default Power Limit | Overdrive Power Limit |
|---|---|---|
| Class 5 | 45 | 45 |
| Class 6 | 60 | 65 |
| Class 7 | 75 | 90 |
| Class 8 | 90 | 120 |
Ports Supporting Overdrive Feature
| ICX Platforms | 2-pair 802.3bt Ports (Type 3) | 4-pair 802.3bt Ports (Type 4) |
|---|---|---|
| ICX 7550-24P | 1 to 24 | None |
| ICX 7550-48P | 1 to 48 | None |
| ICX 7550-24ZP | None | 1 to 24 |
| ICX 7550-48ZP | None | 1 to 48 |
| ICX 7650-48P | 9 to 48 | 1 to 8 |
| ICX 7650-48ZP | 1 to 24 | 25 to 48 |
Power Specifications
The 802.3af (PoE) standard limits power to 15.4 watts (44 to 50 volts) from the power-sourcing device, in compliance with safety standards and existing wiring limitations. Though limited by the 802.3af standard, 15.4 watts of power was ample for most PDs, which consumed an average of 5 to 12 watts of power (IP phones, wireless LAN access points, and network surveillance cameras each consume an average of 3.5 to 9 watts of power). The 802.3at 2008 (PoE+) standard nearly doubles the power, providing 30 watts (52 to 55 volts) from the power-sourcing device.
The PoE power supply provides power to the PoE circuitry block and ultimately to PoE power-consuming devices. The number of PoE power-consuming devices that one PoE power supply can support depends on the number of watts required by each power-consuming device and the capacity of the power supply or power supplies. Each PoE+ port supports a maximum of 30 watts of power per power-consuming device. Each PoH port supports a maximum of 95 watts of power.
As an example, if each PoE power-consuming device attached to a RUCKUS PoE device is budgeted to consume 30 watts of power, one 720- or 748-watt power supply can power up to 24 PoE ports. RUCKUS platforms support either a second power supply or an external power supply (EPS) to augment PoE power budget, depending on the product. Refer to the power supply specifications in the RUCKUS FastIron hardware installation guide for the appropriate RUCKUS device.