A powered device (PD) receives electrical power from Power Sourcing Equipment (PSE) through Ethernet cabling. Power over Ethernet reduces cable runs and allows devices such as IP phones, cameras, and wireless access points to operate where no outlet is nearby. section 10.1.2
PoE delivery protects the connected device through four stages:
- Detection applies low voltage to determine whether the device supports PoE. section 10.1.2
- Classification assesses the PD’s power requirements and reserves the required supply. section 10.1.2
- Startup applies the appropriate voltage; normal operation then monitors current for safe, consistent delivery. section 10.1.2
SW1# show power inline
Available:124.0(w) Used:30.8(w) Remaining:93.2(w) #1
Interface Admin Oper Power Device Class Max
(Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Fa0/1 auto on 15.4 AIR-CAP3502I-E-K9 3 15.4 #2
Fa0/2 auto on 15.4 AIR-CAP3502E-E-K9 3 15.4 #2
Fa0/3 auto off 0.0 n/a n/a 15.4
. . .
#1 Information about the available power budget
#2 The two PDs are class 3, meaning the switch allocates 15.4 watts each.
Use show power inline to inspect the switch power budget, PD status, allocated wattage, device class, and remaining capacity. section 10.1.2
SW1(config)# interface range f0/1-2
SW1(config-if-range)# power inline police #1
SW1(config-if-range)# do show power inline police
Available:124.0(w) Used:30.8(w) Remaining:93.2(w)
Interface Admin Oper Admin Oper Cutoff Oper
State State Police Police Power Power
--------- ------ ---------- ---------- ---------- ------ ----- #2
Fa0/1 auto On errdisable ok 15.4 8.5 #2
Fa0/2 auto On errdisable ok 15.4 8.5
. . .
#1 Enables power policing
#2 The cutoff power is 15.4 watts.
Use power inline police to enable power policing and inspect cutoff and operating power values. section 10.1.2
