Wireless LAN (WLAN)
Also known as: wireless local area network, Wi-Fi network
A wireless LAN is a local area network that connects devices over radio waves instead of cables, using the IEEE 802.11 standards. Access points bridge wireless clients onto the wired network so they behave like any other LAN device.
A WLAN provides the same connectivity as a wired LAN without the cabling. Client devices associate with an access point (AP), which converts between 802.11 wireless frames and 802.3 Ethernet frames and forwards traffic onto the wired infrastructure. The network is identified to users by its SSID (the network name), while the AP's radio interface is identified by a BSSID, typically its MAC address. One AP and its clients form a basic service set (BSS); several APs sharing an SSID so clients can roam between them form an extended service set (ESS).
Because radio is a shared, half-duplex medium, only one device can transmit at a time on a channel. Wireless stations therefore use CSMA/CA — carrier sense multiple access with collision avoidance — listening before transmitting and using acknowledgments, rather than the collision detection used on legacy Ethernet. Wi-Fi operates mainly in the 2.4 GHz band, where channels 1, 6, and 11 are the non-overlapping choices in North America, and in the 5 GHz band, which offers many more non-overlapping channels and less interference at shorter range. Overlapping channel assignments between nearby APs are a common cause of poor performance.
Deployments come in two architectures. Autonomous APs each hold their own configuration and are managed individually, which works for a handful of devices. Lightweight APs hand control functions to a wireless LAN controller (WLC) and tunnel traffic to it using CAPWAP, so configuration, RF management, and security policy are centralized — the practical choice at enterprise scale. Because anyone in range can receive the signal, security is mandatory rather than optional: WPA2 and WPA3 provide encryption and authentication, with personal mode using a shared password (a pre-shared key under WPA2, or SAE under WPA3) and enterprise mode authenticating users individually through 802.1X and a RADIUS server.
The CCNA exam includes wireless fundamentals as a named topic. Be ready to describe AP modes and the WLC architecture, identify SSID and BSSID, explain the difference between the 2.4 GHz and 5 GHz bands and their non-overlapping channels, and compare WPA2 and WPA3 personal and enterprise security options.
Key takeaways
- A WLAN connects devices over 802.11 radio links, with access points bridging wireless clients to the wired network.
- SSID names the network, BSSID identifies an AP radio, and multiple APs sharing an SSID form an extended service set.
- Wireless is a shared half-duplex medium, so stations use CSMA/CA rather than collision detection.
- Channels 1, 6, and 11 are the non-overlapping 2.4 GHz channels; 5 GHz offers more channels with shorter range.
- Lightweight APs centralize configuration and RF management on a wireless LAN controller using CAPWAP.