Linux as wireless access point

I frequently use a script that turns my laptop into an access point. I thought this script might be useful for others, too. Below I also describe what the script does and how to use it.

Requirements

You need the following Debian or Ubuntu packages to run the script:

• hostapd
• dnsmasq-base
• rfkill
• iptables
• procps (for sysctl)

Steps

The script does the following to activate the access point:

1. Activate wireless chip: rfkill unblock wlan
2. Start hostapd as daemon: hostapd -B -P PID_FILE hostapd.conf
3. Add IP address to wireless interface: ip address add IP_ADDRESS brd + dev WIFI_INTERFACE
4. Add rule for network address translation: iptables -t nat -A POSTROUTING -o WAN_INTERFACE -j MASQUERADE
5. Enable IP forwarding (routing): sysctl -q -w net.ipv4.ip_forward=1
6. Start DHCP service: dnsmasq --interface=WIFI_INTERFACE --dhcp-range=IP_RANGE

Running the script

Download accesspoint.sh and hostapd.conf. But before you run the script, you need to

• set parameters in accesspoint.sh:
  • waniface: Interface to the outside world (eg. eth0)
  • wlaniface: Wireless interface (usually wlan0)
  • wlanaddr: IP address of wireless network
  • DHCP pool parameter of dnsmasq command
• set parameters in hostapd.conf:
  • interface: Same wireless interface as in accesspoint.sh
  • ssid: Name of wireless network
  • channel: Integer value (available values depend on country)
  • wpa_passphrase: Key (password) to access the wireless network