show controllers dot11Radio 0
Displays detailed hardware and firmware status of the 802.11 radio interface, used for troubleshooting wireless connectivity issues on Cisco access points and routers.
show controllers dot11Radio 0When to Use This Command
- Verify radio state (up/down) and operational status after a reboot or configuration change.
- Check for hardware errors, CRC failures, or excessive retries that indicate RF interference or faulty hardware.
- Confirm firmware version and bootloader details to ensure compatibility with the IOS image.
- Inspect antenna configuration and signal strength parameters when diagnosing coverage problems.
Command Examples
Basic radio status check
show controllers dot11Radio 0Radio0 - 802.11 Radio State: UP Firmware Version: 12.4(21a)JA1 Bootloader Version: 12.4(21a)JA1 MAC Address: 0011.2233.4455 IP Address: 192.168.1.100 Channel: 6 (2437 MHz) Tx Power: 20 dBm Antenna: Internal Transmit Statistics: Total Packets: 1023456 Total Bytes: 1234567890 Retry Count: 12345 CRC Errors: 67 Deferred: 234 Receive Statistics: Total Packets: 987654 Total Bytes: 987654321 CRC Errors: 12 Overruns: 0 Lost Carrier: 0 Signal Statistics: Noise Floor: -95 dBm Signal Strength: -45 dBm SNR: 50 dB
State: UP indicates the radio is operational. Firmware/Bootloader versions show the code running on the radio. MAC and IP addresses identify the interface. Channel and Tx Power show current RF settings. Transmit/Receive statistics: Retry Count and CRC Errors indicate link quality; high values suggest interference or hardware issues. Signal Statistics: Noise Floor should be low (e.g., -95 dBm), Signal Strength strong (e.g., -45 dBm), and SNR high (e.g., 50 dB) for good performance.
Troubleshooting high error rates
show controllers dot11Radio 0Radio0 - 802.11 Radio State: UP Firmware Version: 12.4(21a)JA1 Bootloader Version: 12.4(21a)JA1 MAC Address: 0011.2233.4455 IP Address: 192.168.1.100 Channel: 11 (2462 MHz) Tx Power: 20 dBm Antenna: Internal Transmit Statistics: Total Packets: 500000 Total Bytes: 600000000 Retry Count: 50000 CRC Errors: 1500 Deferred: 5000 Receive Statistics: Total Packets: 400000 Total Bytes: 480000000 CRC Errors: 2000 Overruns: 100 Lost Carrier: 50 Signal Statistics: Noise Floor: -80 dBm Signal Strength: -60 dBm SNR: 20 dB
High Retry Count (10% of total packets) and CRC Errors (1500 TX, 2000 RX) indicate poor link quality. High Noise Floor (-80 dBm) and low SNR (20 dB) suggest interference. Overruns and Lost Carrier point to possible hardware issues or congestion. This output suggests checking for channel overlap, adjusting power, or inspecting antennas.
Understanding the Output
The output is divided into sections: Radio identity and state, firmware details, MAC/IP, RF configuration, and statistics. The 'State' field is critical; if not UP, the radio is disabled or faulty. Firmware version should match expected release. Channel and Tx Power show current RF settings; ensure channel is not overlapping with nearby APs. Transmit/Receive statistics: Retry Count and CRC Errors are key indicators of link quality—high values (e.g., >5% of total packets) suggest interference, distance, or hardware problems. Deferred packets indicate medium contention. Receive overruns and lost carrier indicate hardware buffer issues or signal loss. Signal Statistics: Noise Floor should be below -90 dBm; higher values indicate interference. Signal Strength should be above -70 dBm for good connectivity. SNR (Signal-to-Noise Ratio) should be above 25 dB; lower values cause retransmissions. Use this command to baseline normal operation and identify degradation over time.
CCNA Exam Tips
CCNA 200-301 may ask which command to verify radio hardware status; 'show controllers dot11Radio 0' is the answer.
Know that 'State: UP' means the radio is operational; any other state indicates a problem.
High CRC errors or retries often point to RF interference or faulty cables/antennas.
The exam might present output with high noise floor and ask for the likely cause (e.g., co-channel interference).
Common Mistakes
Confusing 'show controllers dot11Radio' with 'show interface dot11Radio'—the former shows hardware details, the latter shows Layer 2 stats.
Assuming 'State: UP' guarantees good performance; high error rates can still exist with an UP state.
Ignoring firmware version mismatches which can cause feature incompatibility or bugs.
Practice for the CCNA 200-301
Test your knowledge with hundreds of CCNA practice questions covering all exam domains.
Practice CCNA Questions