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6.3.2. Establishing a Wireless Connection

This section explains how to use NetworkManager to configure a wireless (also known as Wi-Fi or 802.1a/b/g/n) connection to an Access Point.
To configure a mobile broadband (such as 3G) connection, refer to Section 6.3.3, “Establishing a Mobile Broadband Connection”.

Quickly Connecting to an Available Access Point

The easiest way to connect to an available access point is to click on the NetworkManager applet, locate the Service Set Identifier (SSID) of the access point in the list of available networks, and click on it. If the access point is secured, a dialog prompts you for authentication.
NetworkManager tries to auto-detect the type of security used by the access point. If there are multiple possibilities, NetworkManager guesses the security type and presents it in the Wireless security dropdown menu. To see if there are multiple choices, click the Wireless security dropdown menu and select the type of security the access point is using. If you are unsure, try connecting to each type in turn. Finally, enter the key or passphrase in the Password field. Certain password types, such as a 40-bit WEP or 128-bit WPA key, are invalid unless they are of a requisite length. The Connect button will remain inactive until you enter a key of the length required for the selected security type. To learn more about wireless security, refer to Section 6.4.2, “Configuring Wireless Security”.
If NetworkManager connects to the access point successfully, its applet icon will change into a graphical indicator of the wireless connection's signal strength.
Applet icon indicating wireless connection signal strength
A screen shot of the Signal Strength Applet icon indicating wireless connection signal strength
Figure 6.6. Applet icon indicating wireless connection signal strength

Connecting to a Hidden Wireless Network

All access points have a Service Set Identifier (SSID) to identify them. However, an access point may be configured not to broadcast its SSID, in which case it is hidden, and will not show up in NetworkManager's list of Available networks. You can still connect to a wireless access point that is hiding its SSID as long as you know its SSID, authentication method, and secrets.
To connect to a hidden wireless network, click NetworkManager's applet icon and then click Network Settings. The Network window appears. Select the Wireless menu entry and then click to the right of the Network Name to activate the drop-down list. Select Other. The Hidden wireless network dialog window appears.
Hidden wireless network dialog window
A screen shot of NetworkManager's Hidden wireless network dialog window
Figure 6.7. Hidden wireless network dialog window

If you have connected to the hidden network before, use the Connection drop-down list to select it, and click Connect. If you have not, leave the Connection dropdown as New..., enter the SSID of the hidden network, select its Wireless security method, enter the correct authentication secrets, and click Connect.
For more information on wireless security settings, refer to Section 6.4.2, “Configuring Wireless Security”.

Editing a Connection, or Creating a Completely New One

You can create a new connection by clicking on the NetworkManager applet to open its menu.
  1. Click on the NetworkManager applet icon in the Notification Area and click Network Settings. The Network window appears.
  2. Select the Wireless menu entry.
  3. Click to the right of the Network Name to activate the drop-down list.
  4. Select the SSID you want to connect to.
  5. Click the Configure button. The editing a wireless connection window appears.
Editing the newly-created Wireless connection
A screen shot of the NetworkManager's editing a wireless connection window. The Wireless tab has been selected on the left.
Figure 6.8. Editing the newly-created Wireless connection

Configuring the Connection Name, Auto-Connect Behavior, and Availability Settings

Three settings in the Editing dialog are common to all connection types:

Configuring the Wireless Tab

SSID
All access points have a Service Set identifier to identify them. However, an access point may be configured not to broadcast its SSID, in which case it is hidden, and will not show up in NetworkManager's list of Available networks. You can still connect to a wireless access point that is hiding its SSID as long as you know its SSID (and authentication secrets).
For information on connecting to a hidden wireless network, refer to Section 6.3.2, “Connecting to a Hidden Wireless Network”.
Mode
Infrastructure — Set Mode to Infrastructure if you are connecting to a dedicated wireless access point or one built into a network device such as a router or a switch.
Ad-hoc — Set Mode to Ad-hoc if you are creating a peer-to-peer network for two or more mobile devices to communicate directly with each other. If you use Ad-hoc mode, referred to as Independent Basic Service Set (IBSS) in the 802.11 standard, you must ensure that the same SSID is set for all participating wireless devices, and that they are all communicating over the same channel.
BSSID
The Basic Service Set Identifier (BSSID) is the MAC address of the specific wireless access point you are connecting to when in Infrastructure mode. This field is blank by default, and you are able to connect to a wireless access point by SSID without having to specify its BSSID. If the BSSID is specified, it will force the system to associate to a specific access point only.
For ad-hoc networks, the BSSID is generated randomly by the mac80211 subsystem when the ad-hoc network is created. It is not displayed by NetworkManager
MAC address
Like an Ethernet Network Interface Card (NIC), a wireless adapter has a unique MAC address (Media Access Control; also known as a hardware address) that identifies it to the system. Running the ip addr command will show the MAC address associated with each interface. For example, in the following ip addr output, the MAC address for the wlan0 interface (which is 00:1c:bf:02:f8:70) immediately follows the link/ether keyword:
~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 52:54:00:26:9e:f1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.251/24 brd 192.168.122.255 scope global eth0
    inet6 fe80::5054:ff:fe26:9ef1/64 scope link
       valid_lft forever preferred_lft forever
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:1c:bf:02:f8:70 brd ff:ff:ff:ff:ff:ff
    inet 10.200.130.67/24 brd 10.200.130.255 scope global wlan0
    inet6 fe80::21c:bfff:fe02:f870/64 scope link
       valid_lft forever preferred_lft forever
A single system could have one or more wireless network adapters connected to it. The MAC address field therefore allows you to associate a specific wireless adapter with a specific connection (or connections). As mentioned, you can determine the MAC address using the ip addr command, and then copy and paste that value into the MAC address text-entry field.
MTU
The MTU (Maximum Transmission Unit) value represents the size in bytes of the largest packet that the connection will use to transmit. If set to a non-zero number, only packets of the specified size or smaller will be transmitted. Larger packets are broken up into multiple Ethernet frames. It is recommended to leave this setting on automatic.

Saving Your New (or Modified) Connection and Making Further Configurations

Once you have finished editing the wireless connection, click the Apply button and NetworkManager will immediately save your customized configuration. Given a correct configuration, you can successfully connect to your the modified connection by selecting it from the NetworkManager Notification Area applet. See Section 6.2.1, “Connecting to a Network” for details on selecting and connecting to a network.
You can further configure an existing connection by selecting it in the Network Connections window and clicking Edit to return to the Editing dialog.
Then, to configure: