25/08/2025
Cisco Catalyst Switch Front Panel LEDs
1. SYST (System Status
* Off → Switch is powered off.
* Green → Switch is powered on and running normally.
* Amber → The switch has a hardware or software fault.
If your access-layer switch in the office is green, users can connect to the network. If it turns amber, the switch may have a failed power supply or boot issue, and users on that floor may lose connectivity.
2. RPS (Redundant Power Supply)
* Off → No RPS connected.
* Green → RPS is connected and ready.
* Blinking Green → Switch is running on RPS (main power failed).
* Amber → RPS is connected but has a fault.
In a data center, if the building power fails but your switch has RPS connected, the RPS LED blinks green, showing the switch is now running on backup power. This keeps servers connected to the network without downtime.
3. MASTR (Stack Master)
* Green → This switch is the master in the stack.
* Off → This switch is not the master.
In a core stack of 4 switches, only one switch (master) controls configuration and management. If the master fails, another switch takes over to keep the network stable.
4. STAT (Port Status) – Default Mode
* Green (solid) → Port is connected.
* Green (blinking) → Port is sending/receiving traffic.
* Amber → Port is blocked (e.g., STP loop prevention) or has a fault.
* Off → No device connected.
> A server NIC connected → Port LED solid green.
> When the server starts handling requests → LED blinks green.
> If spanning tree blocks a redundant uplink → Port LED amber.
5. DUPLX (Duplex)
* Green → Port is in Full Duplex (send and receive at same time).
* Off → Port is in Half Duplex.
> An uplink from access switch to core switch runs at Full Duplex, allowing smooth two-way communication.
> If connected to an old printer NIC running Half Duplex, LED stays off, which can cause collisions and slower performance.
6. SPEED
* Off → 10 Mbps.
* Green → 100 Mbps.
* Blinking Green → 1 Gbps.
> Old VoIP phone port shows green = 100 Mbps.
> Modern laptop port shows blinking green = 1 Gbps.
7. STACK
* Green → Switch is part of a stack.
* Blinking Green → Stack communication is active.
* Off → Not stacked.
In a large office, 3 switches are stacked together. All behave as one logical switch for easier management. Each stacked member shows green.
8. PoE (Power over Ethernet)
* Green → Port is providing PoE power.
* Amber → Port requested PoE but switch denied (maybe power limit reached).
* Off → No PoE being delivered.
> An IP Phone connected → PoE LED green.
> If too many Access Points are powered and budget is exceeded → New AP port shows amber.
🔘 Mode Button
* Press to toggle what the port LEDs display.
* STAT → port connectivity and traffic.
* DUPLX → duplex mode.
* SPEED → link speed.
* PoE → power status.
✅ This is how network engineers use LEDs in real environments to quickly troubleshoot without logging into the switch.
