Difference between revisions of "Software access point"

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m (Bridge Setup: Added a special case for an existing bridge.)
m (Bridge Setup: fixed note - that is entirely optional, no "should"...)
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If you use [[netctl]], see [[Bridge with netctl]] for details (just do not add {{ic|tap0}} used in that example).
If you use [[netctl]], see [[Bridge with netctl]] for details (just do not add {{ic|tap0}} used in that example).
(If you have an existing bridge, used by a virtual machine for example, then you should reuse that one.)
{{Tip|You may wish to reuse an existing bridge, if you have one (e.g. used by a virtual machine).}}
=== NAT Setup ===
=== NAT Setup ===

Revision as of 13:18, 31 January 2014

A software access point is used when you want your computer to act as an wifi access point for the local wireless network. It saves you the trouble of getting a separate wireless router.


  • A nl80211 compatible wireless device (e.g. ath9k)


Setting up an access point comprises two main parts:

  • Setting up the wifi link layer, so that wireless clients can associate to your computer's "software access point" and send/receive IP packets from/to your computer; this is what the hostapd package will do for you.
  • Setting up the network configuration on you computer, so that your computer will properly relay IP packets from/to its own Internet connection from/to wireless clients.

Wifi Link Layer

The actual Wifi link is established via the hostapd package (available in the official repositories). The package has WPA2 support.

Adjust the options in hostapd configuration file if necessary. Especially, change the ssid and the wpa_passphrase. See hostapd Linux documentation page for more information.

wpa_pairwise=TKIP CCMP

For automatically starting hostapd, enable the hostapd.service.

Note: If you have a card based on RTL8192CU chipset, you will have to build this patched version of hostapd and replace driver=nl80211 with driver=rtl871xdrv in the hostapd.conf file.

Network configuration

There are two basic ways for implementing this:

  1. bridge: create a network bridge on your computer (wireless clients will appear to access the same network interface and the same subnet that's used by your computer)
  2. NAT: with IP forwarding/masquerading and DHCP service (wireless clients will use a dedicated subnet, data from/to that subnet is NAT-ted -- similar to a normal WiFi router that's connected to your DSL or cable modem)

The bridge approach is simpler, but it requires that any service that's needed by your wireless clients (like, DHCP) is available on your computers external interface. That means it will not work if you have a dialup connection (e.g., via PPPoE or a 3G modem) or if you're using a cable modem that will supply exactly one IP address to you via DHCP.

The NAT aproach is more versatile, as it clearly separates wifi clients from your computer and it's completely transparent to the outside world. It will work with any kind of network connection, and (if needed) you can introduce traffic policies using the usual iptables approach.

Of course, it is possible to combine both things. For that, studying both articles would be necessary. Example: Like having a bridge that contains both an ethernet device and the wireless device with an static ip, offering DHCP and setting NAT configured to relay the traffic to an additional network device - that can be ppp or eth.

Bridge Setup

You need to create a network bridge and add your network interface (e.g. eth0) to it. You should not add the wireless device (e.g. wlan0) to the bridge; hostapd will add it on its own.

If you use netctl, see Bridge with netctl for details (just do not add tap0 used in that example).

Tip: You may wish to reuse an existing bridge, if you have one (e.g. used by a virtual machine).

NAT Setup

See Internet Sharing for details.

On that article, the device connected to the lan is net0. That device would be in this case your wireless device (e.g. wlan0).


create_ap script combines hostapd, dnsmasq and iptables to create a NATed Access Point.


WLAN is very slow

This could be caused by low entropy. Consider installing haveged.

NetworkManager is interfering

hostapd may not work, if the device is managed by NetworkManager. You can mask the device:


See also