4120 Series System LEDs

System status LEDs are located on the front of the switch. The following figure shows the status LEDs for 4120 Series switches:

Table 1. 4120 Series Port LEDs
Label	Function	Color/State	Port State
SYS	System status LED (Legacy MGMT function)	Green Flash slowly	POST Passed, normal operation, blinks on standalone switch, stack master, and backup nodes in a stack; off for standby nodes in a stack
		Green Blinking	POST in progress
		Amber Blinking	POST failed or overheat
P1/P2	PSU status LEDs	Solid Green	Normal operation
		Amber Blinking	Input or output power failures
		Off	Not present
SPD STK	Speed status LED Stacking status LED	SPD Solid Green	Speed mode
		STK Solid Green	Stacking mode
		All off	Normal mode
FAN	Fan status LEDS	Solid Green	Normal operation
FAN	Fan status LEDS	Amber Blinking	Fan failure
BT	Bluetooth Status LED	Green Blinking	Bluetooth pairing in progress
		Solid Green	Bluetooth connected
		Off	Bluetooth not connected
LOC	Locator LED	Blue Blinking	Locator function

Port LEDs can display in three different modes: SYS (the default mode), SPD (speed) and STK (stacking). The Mode button cycles through the three display modes. In the default SYS mode, SPD and STK are off. The port LEDs enter SPD display mode, indicated by the SPD LED, after pressing the Mode button one time. SPD mode helps to determine the operational speed of a port. The port LEDs enter the STK display mode, indicated by the STK LED, after pressing the Mode button a second time. STK mode is used to indicate slot presence and slot number through the first eight port LEDs. SPD and STK display modes expire after 30 seconds, and the display mode reverts back to the default SYS mode. A long press of the Mode button when in any mode other than STK mode initiates Bluetooth pairing.

Port LEDs in Default (SYS) Mode

In the default SYS mode, SPD and STK are OFF. Port status displays behavior for link, traffic, and PoE as described in the following table:

Table 2. Port LEDs in SYS Mode (default)
Color/State	Meaning
Solid Green	Link is OK; port is not powered
Solid Amber	Link is OK; port is powered; no traffic
Blinking Green	Link is OK and transmitting packets; port is not powered
Blinking Amber	Link is OK and transmitting packets; port is powered
Slow Blinking Amber	No link, or disabled port; port is powered
Alternating Amber and Green	Port has a power fault
Off	Port is not powered, has no link, or is disabled

Port LEDs in SPD Mode

SPD mode helps to determine the operational speed of a port.

Table 3. Port LEDs in SPD Mode
Color/State	Speed
Slow Blinking Green	10Mbps
Fast Blinking Green	100Mbps
Solid Green	1000Mbps
Slow Blinking Amber	2.5Gbps
Slow Blinking Green	10Gbps
Fast Blinking Green	25Gbps
Fast Blinking Green	100Gbps

Port LEDs in STK Mode

STK mode indicates slot presence and slot number through the first eight port LEDs. Pressing the Mode button for 5 seconds when in STK mode initiates InstaStack auto-stacking.

Table 4. Port LEDs in STK Mode
Port 1-8 Color/State	Stacking Indication
Steady green	Slot corresponding to the port number of the LED is present
Blinking green	This slot has slot number corresponding the port number of the blinking LED

Management Port LEDs

100/1000Base-T RJ-45 Management port on the rear panel includes two LED located on each side of the RJ-45 port. The LED on the right side is labeled Link (for link status) and the LED on the left side is labeled Act (for port activity). The following table describes the meaning of the colors and states for the LEDs.

Table 5. Management Port LEDs
Right-side LED		State
Link	Green	Link up
Link	Off	No link up or port disable
Left-side LED		State
Act	Blinking Green	Packet transmitting or receiving
Act	Off	No packet transmitting or receiving

QSFP28 Port LEDs in SYS Mode (default)

Each QSFP28 port has four green LEDs. The following table describes the states for the LEDs.

Table 6.
Location	Port Configuration	LEDs	State	Description
Partionable Ports U1, U2	4 x 10 Gb or 4 x 25 Gb (partitioned)	All 4 LEDs Green	Solid light	The port has a link.
	4 x 10 Gb or 4 x 25 Gb (partitioned)	All 4 LEDs Green	Blinking	Port is transmitting and/or receiving.
	1 x 100 Gb (not partitioned)	1st LED is Green, LEDs 2,3,4 are off	Solid light	The port has a link.
	1 x 100 Gb (not partitioned)	1st LED is Green, LEDs 2,3,4 are off	Blinking	Port is transmitting and/or receiving.
	Off or not present.	N/A	Light is off.	No link or the port is disabled.

QSFP28 Port LEDs in SPD Mode

Table 7.
Location	Port Configuration	LEDs	State	Description
Partionable Ports U1, U2	4 x10 Gb (partitioned)	All 4 LEDs Green	Slow blinking	The port has a 10 Gbps link.
	4 x 25 Gb (partitioned)	All 4 LEDs Green	Fast blinking	The port has a 25 Gbps link.
	1 x 100 Gb (not partitioned)	1st LED is Green, LEDs 2,3,4 are off	Fast blinking	The port has a 100 Gbps link.
	Off or not present.	N/A	Light is off.	No link or the port is disabled.

Locator LED

The blue LED labeled LOC on the front panel is the locator LED, which is controlled by using the CLI commands

[enable | disable] led locator.