Configuring Wireless Networking

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On your Linux laptop, the PCMCIA or PC Card manager should recognize the wireless network card and load the appropriate driver for the card. The wireless network card is treated like another Ethernet device and assigned a device name such as eth0 or ethl. If you already have an Ethernet card in the laptop, that card gets the eth0 device name, and the wireless PC card is named the ethl device.

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You do have to configure certain parameters to enable the wireless network card to communicate with the wireless access point. For example, you have to specify the wireless network name assigned to the access point—and the encryption settings must match those on the access point. You can usually configure everything using the graphical network configuration tool.

Follow these steps to configure and activate the wireless network connection on your Fedora Linux system:

1. Select Desktop O System Settings O Network from the GNOME desktop; then click New on the toolbar. The Add New Device Type window appears.

2. Click to select Wireless connection from the Device Type list and then click Forward.

3. Select the wireless device (this should be automatically detected and listed as a choice) and click Forward. The Configure Wireless Connection window appears.

4. Configure the wireless connection (see Figure 13-8). In particular, set the Mode to Managed, specify the name of the wireless network (the one you want to connect to), and set the encryption key, if any. Click Forward. The Configure Network Settings window appears.

Figure 13-8: Configure the Wireless Connection from This Window.

5. Set the option for getting the IP address to DHCP (a protocol for obtaining network configuration parameters, including IP addresses from a server on the network). Click Forward. The Create Wireless Device window appears.

6. Check the configuration information and if it's correct, click Apply to complete the wireless Ethernet setup. You return to the Network Configuration tool's main window.

7. Select the new wireless device and click the Activate button. If all goes well, the wireless network should be up and running after a few moments.

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The Network Configuration tool saves the wireless network settings in a text file whose name depends on the wireless network device name. If the wireless network device name is eth0, the configuration is stored in the text file /etc/sysconfig/network-scripts/ifcfg-eth0. If the wireless device name is eth1, the file is /etc/sys config/network-scripts/ifcfg-eth1. This configuration file contains various settings for the wireless network card. Table 13-2 explains the meaning of the settings. Here is a slightly edited version of the /etc/sysconfig/network-scripts/ ifcfg-eth1 file from my laptop PC running Fedora:

IPV6INIT=no

USERCTL=no

PEERDNS=yes

TYPE=Wireless

DEVICE=eth1

HWADDR=00:02:2d:8c:f9:c4

BOOTPROTO=dhcp

ONBOOT=no

DHCP_HOSTNAME=

NAME=

ESSID='HOME' CHANNEL=6 MODE=Managed RATE=auto

The encryption key is stored separately. For a wireless Ethernet card whose device name is eth1, the encryption key is stored in the /etc/sysconfig/network-scripts/keys-eth1 file. For example, here is what this file contains for my example:

KEY=AECFA00F03

Note that the key has 10 hexadecimal digits for a 40-bit key (for example, 1fdf-3fde-fe) or 26 hexadecimal digits for a 104-bit key. The keys are, in fact, 64-bit and 128-bit, but the encryption algorithm automatically generates 24 bits of the key, so you need to specify only the remaining bits. Needless to say, the longer the key, the more secure the encryption.

Table 13-2: Settings in the Configuration File for a Wireless Ethernet Network Interface

Parameter Description

BOOTPROTO The name of the protocol to use to get the IP address for the interface. Should be either dhcp or bootp for an Ethernet interface.

CHANNEL Channel number (between 1 and 14 in the U.S. and Canada). Must be the same as that set for the wireless access point.

DEVICE The device name for the wireless Ethernet network interface (eth0 for the first interface, eth1 for second, and so on)

Parameter

Description

ESSID Extended Service Set (ESS) Identifier, also known as the wireless network name. It is case sensitive and must be the same as the name specified for the wireless access point. Provide the name within single quotes (for example, 'HOME').

HWADDR The hardware address (also called the MAC address) of the wireless network card

(six pairs of colon-separated hexadecimal numbers; for example, 00:02:2d:8c:f9:c4). The wireless card's device driver automatically detects this address.

IPV6INIT When set to yes, this parameter initializes IPv6 configuration for the wireless interface. Set it to no if you are not using IPv6.

MODE The mode of operation of the wireless network card. Set to Managed for a typical network that connects through a wireless access point.

NAME A nickname for your wireless network. If you don't specify it, the host name is used as the nickname.

ONBOOT Set to yes to activate the wireless interface at boot time; otherwise set to no.

PEERDNS Set to yes to enable the interface to modify your system's / etc/resolv.conf file to use the DNS servers obtained from the DHCP server (this is the same server that provides the IP address for the interface). If you set this to no, the /etc/resolv.conf file is left unchanged.

RATE Bit rate for the wireless connection (set to one of 1M, 2M, 5.5M, 11M, or auto).

The M means Mbps or a million bits per second. Set to auto to use the maximum possible transmission rate.

TYPE Set to Wireless for wireless network interface.

USERCTL When set to yes, a non-root user can control the device. Set it to no so that only root can control the device.

Now, the wireless interface should be working properly. To check the interface status, type the following command:

iwconfig

Here's a typical output on my Linux laptop:

lo no wireless extensions.

eth0 IEEE 802.11-DS ESSID:"HOME" Nickname:"localhost.localdomain"

Mode:Managed Frequency:2.437GHz Access Point: 00:30:AB:06:2E:5D Bit Rate=11Mb/s Tx-Power=15 dBm Sensitivity:1/0 Retry limit:4 RTS thr:off Fragment thr:off Encryption key:AECF-A00F-03 Power Management:off

Link Quality:66/0 Signal level:-27 dBm Noise level:-93 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0

Here the eth0 interface refers to the wireless network card. I have edited the encryption key and some other parameters, but the sample output shows what you should see when the wireless link is working.

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