Cisco "show controllers" Command Explained
show controllers — shows low-level hardware and physical-layer detail for an interface — cable type detected, clock rate, and signaling information below what show interfaces reports. Runs in privileged EXEC mode.
Syntax and common variants
| Variant | Purpose |
|---|---|
show controllers serial 0/0/0 | Physical-layer detail for a serial interface |
show controllers gi0/1 | Hardware-level detail for an Ethernet port |
Reading the output
| Output / element | Meaning |
|---|---|
DCE / DTE cable detected | Which end of a serial link this router is (DCE provides clocking) |
clock rate | The configured/detected clocking speed on a serial link |
When to use it
Mostly used for serial/WAN interfaces to diagnose physical-layer issues show interfaces can't reveal — like confirming which end is DCE (and therefore needs the clock rate command) versus DTE. Less common with modern Ethernet-based WANs but still tested in CCNA WAN topics. Browse more in the command reference or practise in the free labs.
Frequently asked questions
What is the difference between show controllers and show interfaces?
show interfaces reports Layer 1/2 status and counters; show controllers reveals lower-level hardware detail like cable type and clocking, especially on serial interfaces.
What is a DCE vs DTE cable?
On a serial link, the DCE end provides clocking (and needs the clock rate command); the DTE end receives timing from the DCE. show controllers reveals which end you're on.
Why would I need this command?
Diagnosing serial/WAN link issues where the interface is down/down and you need to confirm cable type or clocking configuration.
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