Wireless networks

July 19, 2025 · in CompTIA Network+ (Dion Training)

Wireless network types

Ad hoc / IBSS: devices connect peer-to-peer with no AP. Quick temporary setups.
Infrastructure: devices join wired LANs through APs. The BSSID is the AP’s MAC by default, the SSID is the network name, and an ESS is multiple APs sharing one SSID (ESSID) so clients roam between them without dropping.
Point-to-point: high-gain antennas link two fixed sites with dedicated bandwidth where cabling isn’t feasible.
Mesh: nodes interconnect with self-healing paths. Good for large deployments where cable is impractical.

Autonomous APs run standalone (small setups); lightweight APs offload processing to a central wireless controller (big networks).

Antennas

Omnidirectional: equal power in all directions, broad coverage, the default in APs and phones.
Unidirectional: energy focused one way for long distance or limiting bleed-over; patch antennas suit building-to-building links.
Parabolic: curved-dish unidirectional for microwave and satellite point focus.
Yagi: high-gain narrow-beam directional for long-distance point-to-point.

Frequency bands

2.4 GHz: long range, good penetration. Channels 1-14 exist (region-dependent), and only 1, 6, and 11 don’t overlap.
5 GHz: faster, shorter range. Up to 24 non-overlapping channels.
6 GHz: fastest, shortest, least penetration. Up to 59 channels (20/40/80/160 MHz widths).

Channel bonding merges adjacent channels for more bandwidth but more interference exposure.

802.11h (European compliance): DFS monitors for radar, and TPC dials transmit power down to the minimum needed. Band steering pushes clients to the best band automatically.

802.11 standards

a: 5 GHz, 54 Mbps
b: 2.4 GHz, 11 Mbps
g: 2.4 GHz, 54 Mbps
n (Wi-Fi 4): 2.4/5 GHz, 300/600 Mbps
ac (Wi-Fi 5): 5 GHz, 6.9 Gbps
ax (Wi-Fi 6/6E): 2.4/5/6 GHz, 9.6 Gbps

MIMO (n) uses multiple antennas at once and behaves like a hub. MU-MIMO (ac/ax) serves multiple users simultaneously and behaves like a switch.

Band membership for the exam: 2.4 GHz is b/g/n/ax, 5 GHz is a/n/ac/ax, 6 GHz is ax only.

Wireless security

PSK is simple but unscalable: one shared secret, zero individual accountability. Enterprise auth (802.1X + RADIUS) gives per-user credentials.

WEP (1999): RC4 with a 24-bit IV in plaintext. Crackable in minutes (Aircrack-ng).
WPA: RC4 + TKIP (48-bit), MIC. The stopgap fix for WEP.
WPA2 (2004, 802.11i): AES + CCMP. 128-bit AES typical, in personal or enterprise mode.
WPA3 (2018): AES + SAE. Dragonfly key exchange, forward secrecy, slows brute force.

WPS (PIN and push-button setup) is brute-forceable. Disable it.

More depth on WPA3’s SAE handshake in my Security+ notes.

Captive portals

A webpage intercepting new connections on guest and public Wi-Fi (hotels, airports, coffee shops) for authentication, policy acceptance, and data collection.

Design for easy UX, data-protection compliance (GDPR), and cross-device testing.