How WLAN Clients Locate Access Points – Understanding Passive and Active Scanning

In this lesson, I’ll explain how a client device locates a wireless LAN (WLAN) to connect to. This process involves specific messages or frames exchanged between the client and access point (AP) and can happen in two main ways: passive scanning and active scanning. Let’s explore how each method works and the different frames involved in helping clients find and connect to a WLAN.

Locating a WLAN: Passive and Active Scanning Methods

WLAN clients use passive and active scanning to locate access points. These methods allow clients to discover available networks and select the one with the best signal for optimal connectivity. Understanding these scanning processes helps you configure WLANs effectively, ensuring clients can easily locate and connect to your network.

Before diving into the details, it’s important to note that clients and access points exchange specific frames to establish communication and locate WLANs. The primary frames involved are beacon frames, probe request frames, and probe response frames. Let’s go over each of these frames and how they function in the WLAN location process.

Beacon Frames

Beacon frames are broadcasted by the access point multiple times per second, serving as a “beacon” for client devices looking for a WLAN. These frames contain crucial information about the access point, such as the SSID (network name), signal strength, and other relevant data that helps the client recognize and locate the WLAN.