Wireless

WiFi management — iw, wpa_supplicant, iwctl, and wireless interface diagnostics.

Interface Discovery

List all wireless interfaces and their current state

iw dev

Show wireless interface capabilities — supported bands, modes, HT/VHT

iw phy phy0 info

Check if the wireless card is hard or soft blocked

rfkill list wifi

Unblock a soft-blocked wireless interface

sudo rfkill unblock wifi

Show the regulatory domain — affects available channels and tx power

iw reg get

Set the regulatory domain to US (affects legal channels and power limits)

sudo iw reg set US

Scanning & Signal Analysis

Scan for available networks — shows SSID, channel, signal, security

sudo iw dev wlan0 scan | awk '/SSID:|signal:|freq:|capability:|RSN/'

Quick scan using NetworkManager — cleaner output for interactive use

nmcli device wifi list

Rescan and refresh the network list

nmcli device wifi rescan && nmcli device wifi list

Show signal strength for connected network — RSSI in dBm

iw dev wlan0 link

Interpreting signal strength (RSSI reference)

-30 dBm = Excellent (right next to AP)
-50 dBm = Very good
-60 dBm = Good (reliable for most uses)
-67 dBm = Minimum for VoIP/video
-70 dBm = Weak (web browsing OK)
-80 dBm = Very weak (connection drops likely)
-90 dBm = Unusable

Monitor signal strength continuously — one line per second

watch -n1 'iw dev wlan0 link | grep signal'

Connecting with NetworkManager

Connect to an open network

nmcli device wifi connect "SSID_NAME"

Connect to WPA2-Personal with password

nmcli device wifi connect "SSID_NAME" password "passphrase"

Connect to a hidden SSID

nmcli device wifi connect "HIDDEN_SSID" password "passphrase" hidden yes

Show saved connection profiles

nmcli connection show

Disconnect from the current network

nmcli device disconnect wlan0

Delete a saved connection profile

nmcli connection delete "SSID_NAME"

Show full details of a connection profile — useful for debugging 802.1X

nmcli connection show "SSID_NAME" | grep -E '802-1x|wifi-sec|ssid'

WPA Supplicant (Manual / 802.1X)

Generate a wpa_supplicant config for WPA2-Personal

wpa_passphrase "SSID_NAME" "passphrase" > /etc/wpa_supplicant/wpa_supplicant-wlan0.conf

Connect using wpa_supplicant directly — foreground for debugging

sudo wpa_supplicant -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant-wlan0.conf -D nl80211

EAP-TLS config block for 802.1X wireless (Cisco C9130AX / WLC)

network={
    ssid="Corporate_SSID"
    key_mgmt=WPA-EAP
    eap=TLS
    identity="user@domain"
    ca_cert="/etc/ssl/certs/ca-chain.pem"
    client_cert="/etc/ssl/certs/client.pem"
    private_key="/etc/ssl/private/client.key"
    private_key_passwd="<REDACTED>"
}

Check wpa_supplicant status — shows EAP state and authentication progress

wpa_cli -i wlan0 status

Debugging Wireless Issues

Monitor wireless events in real time — association, disassociation, auth

sudo iw event -t

Watch kernel and NetworkManager logs for wifi issues

journalctl -u NetworkManager --since "5 minutes ago" --no-pager | grep -i wifi

Check for firmware loading errors on the wireless driver

dmesg | grep -iE 'iwlwifi|ath|firmware|wlan'

Show the wireless driver in use and its module parameters

ethtool -i wlan0

Show wireless statistics — retries, failures, beacon loss

iw dev wlan0 station dump

Channel Selection Reference

Show which channels your card supports and their current status

iw phy phy0 channels

Channel planning reference — non-overlapping 2.4 GHz channels

2.4 GHz non-overlapping: 1, 6, 11
5 GHz DFS-free (U-NII-1): 36, 40, 44, 48
5 GHz DFS (U-NII-2): 52-144 (radar detection required)
5 GHz high (U-NII-3): 149, 153, 157, 161, 165

Legacy Tools

Show interface status with iwconfig — deprecated but still common

iwconfig wlan0

Set tx power (if regulatory domain allows) — iwconfig legacy syntax

sudo iwconfig wlan0 txpower 20

hostapd (Access Point Mode)

Minimal hostapd config for a software AP — testing/lab use

interface=wlan0
driver=nl80211
ssid=LabAP
hw_mode=g
channel=6
wmm_enabled=0
auth_algs=1
wpa=2
wpa_passphrase=testpassword
wpa_key_mgmt=WPA-PSK
rsn_pairwise=CCMP

Start hostapd in foreground for debugging

sudo hostapd /etc/hostapd/hostapd.conf

Start hostapd as a daemon

sudo hostapd -B /etc/hostapd/hostapd.conf