Cisco 500 Series Administration Manual page 248

Port Management: PoE
PoE on the Device
!
CAUTION
Cisco 500 Series Stackable Managed Switch Administration Guide
The following can be configured:
• Maximum power a PSE is allowed to supply to a PD.
• During device operation, to change the mode from Class Power Limit to
Port Limit and vice versa. The power values per port that were configured
for the Port Limit mode are retained.
Changing the mode from Class Limit to Port limit and vice versa when
NOTE
the device is operational forces the PD to reboot.
• Maximum port limit allowed as a per-port numerical limit in mW (Port Limit
mode).
• To generate a trap when a PD tries to consume too much and at what
percent of the maximum power this trap is generated.
The PoE-specific hardware automatically detects the PD class and its power limit
according to the class of the device connected to each specific port (Class Limit
mode).
If at any time during the connectivity, an attached PD requires more power from
the device than the configured allocation allows (no matter if the device is in Class
Limit or Port Limit mode), the device does the following:
• Maintains the up/down status of the PoE port link
• Turns off power delivery to the PoE port
• Logs the reason for turning off power
• Generates an SNMP trap
When a lower voltage PoE device is connected to the SG500 series
NOTE
device with PoE, and connected via PoE enabled ports on both ends of the
connection, the lower voltage device lose its ability to power any powered
device. To avoid this condition, either disable PoE support on the SG500 or
use a non-PoE port.
Consider the following when connecting switches capable of supplying PoE:
The PoE models of the Sx200, Sx300, and SF500 series switches are PSE capable
of supplying DC power to attaching PDs. These devices include VoIP phones, IP
cameras, and wireless access points. The PoE switches can detect and supply
power to pre-standard legacy PoE PDs. Due to the support of legacy PoE, it is
possible that a PoE device acting as a PSE may mistakenly detect and supply
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