With hostapd you can quickly and easily run an access point. Sometimes it can be useful to diffuse a temporary SSID and/or analyze the traffic from a specific device with Wireshark.

Inspiration is taken from Matt Brown’s mitmrouter project which configures the entire network stack manually. Here we leverage NetworkManager instead.

Hardware considerations

As usual when messing around with WLAN, adapter support is hit-or-miss:

  • Alfa Network AWUS036AXML adapter, based on a MediaTek MT7921AUN chipset works well.
  • TP-Link Archer T3U adapter, based on a Realtek RTl8812BU chipset did not send any beacons out. Not great for an access point.
  • Intel AX200 PCIe card works, but you end up with the international regulatory domain (see the OTA WLAN capture article for more details).

Connected devices need at least to receive an IP address. They may also connect to internet. We’re going to create bridge0 interface with NetworkManager and apply connection sharing on it.

nmcli connection add type bridge \
    ifname bridge0 \
    connection.id bridge0 \
    connection.autoconnect yes \
    ipv4.method shared \
    ipv4.addresses 172.31.255.1/24 \
    ipv6.method disabled \
    bridge.stp no \
    bridge.multicast-snooping no
    
nmcli con up bridge0

Access point

Create a hostapd.conf file with following content.

interface=wlan0
bridge=bridge0
ssid=IOT
country_code=CH
hw_mode=g
channel=6
wpa=2
wpa_passphrase=ConnectingIOT
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP
ieee80211n=1
#ieee80211w=1

Avoid NetworkManager to interfer with your chosen AP interface.

$ nmcli device set wlan0 managed no

Start hostapd.

sudo hostapd hostapd.conf

Verify that your SSID is visible.

nmcli dev wifi