iwlist

The iwlist command is a part of the wireless-tools package on Linux systems and is used for querying wireless network interfaces for various information. It's often used in conjunction with the iwconfig command, which is used to configure wireless network interfaces.

Basic Usage

To use iwlist, you typically need to specify the wireless interface you want to query and the type of information you want to retrieve.

Common Commands and Options

1. Scan for Wireless Networks

• Command:

  iwlist <interface> scan

• Description: Scans for available wireless networks and displays information about each network.

• Example:

  iwlist wlan0 scan

• Example Output:

  wlan0     Scan completed :
            Cell 01 - Address: 00:11:22:33:44:55
                      ESSID:"NetworkName"
                      Mode:Master
                      Frequency:2.412 GHz (Channel 1)
                      Quality=70/70  Signal level=-30 dBm  
                      Encryption key:on
                      IE: IEEE 802.11i/WPA2 Version 1
                      ...

2. Show Wireless Interface Information

• Command:

  iwlist <interface> <info_type>

• Description: Displays various types of information about the wireless interface. Common info types include:

  • scan: Shows available networks (already covered).

  • freq: Displays the available frequencies.

  • power: Shows power settings.

• Example:

  iwlist wlan0 freq

• Example Output:

  wlan0     2.412 GHz
            2.417 GHz
            2.422 GHz
            ...

3. Display Detailed Wireless Network Information

• Command:

  iwlist <interface> scan | grep -i <keyword>

• Description: Allows filtering the scan results to find specific information.

• Example:

  iwlist wlan0 scan | grep -i "SSID"

• Example Output:

  SSID:"NetworkName"
  SSID:"AnotherNetwork"

4. Display Signal Strength and Quality

• Command:

  iwlist <interface> scan | grep -E "Quality|Signal level"

• Description: Filters the scan results to display only the signal strength and quality of networks.

• Example:

  iwlist wlan0 scan | grep -E "Quality|Signal level"

• Example Output:

  Quality=70/70  Signal level=-30 dBm  
  Quality=40/70  Signal level=-60 dBm

Important Concepts

• ESSID: Extended Service Set Identifier. It is the name of the wireless network.

• Mode: Indicates the mode of operation, such as Master (AP) or Managed (Client).

• Frequency: The frequency on which the network operates.

• Quality: Indicates the signal quality of the network, typically a percentage.

• Signal Level: The strength of the signal received from the network, measured in dBm (decibels relative to a milliwatt).

• Encryption Key: Indicates whether the network is secured with encryption.

Example Scenarios

1. Finding Available Networks:

   • Use iwlist to scan for and list all available wireless networks in the vicinity.

2. Checking Network Strength:

   • Evaluate the signal strength and quality of nearby networks to determine the best one to connect to.

3. Determining Frequency Bands:

   • Check which frequency bands are in use by scanning for available frequencies.

4. Troubleshooting Wireless Connections:

   • Analyze scan results to troubleshoot connectivity issues or find out why a network might not be appearing.

Conclusion

The iwlist command is a powerful tool for querying wireless network interfaces and gathering detailed information about available networks and their characteristics. By understanding and using iwlist, network administrators and users can effectively manage and troubleshoot wireless network connections.