Domain 2 of 5 · Chapter 3 of 4

Wireless Networks

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Included in this chapter:

  • Standards, generations, and bands
  • Channels, width, and interference
  • SSID, BSS/ESS, network types, and roaming
  • Securing the WLAN: WPA2, WPA3, Personal vs Enterprise
  • Antennas, placement, and exam-pattern recognition

IEEE 802.11 wireless standards (Network+ generation table)

Standard (Wi-Fi name)Band(s)Max throughputChannel widthNotable feature
802.11a5 GHz54 Mbps20 MHzEarly 5 GHz, less range
802.11b2.4 GHz11 Mbps22 MHzLong range, low speed
802.11g2.4 GHz54 Mbps20 MHzb-compatible, faster
802.11n (Wi-Fi 4)2.4 and 5 GHz600 Mbps20 / 40 MHzMIMO, channel bonding
802.11ac (Wi-Fi 5)5 GHz~6.9 Gbpsup to 160 MHzMU-MIMO, 256-QAM
802.11ax (Wi-Fi 6 / 6E)2.4 / 5 (6E adds 6) GHz~9.6 Gbpsup to 160 MHzOFDMA, 1024-QAM
802.11be (Wi-Fi 7)2.4 / 5 / 6 GHz~23 Gbpsup to 320 MHzMLO, 4096-QAM

Decision tree

What matters mostfor the band?Range / wallsSpeedCleanest spectrum2.4 GHzchannels 1 / 6 / 11 only20 MHz width5 GHzmore channels, wider40 / 80 / 160 MHz6 GHzWi-Fi 6E / Wi-Fi 7 onlymost spectrum, least rangeNeed per-user,revocable accounts?then choose securityYesNo (shared key)WPA3 / WPA2-Enterprise802.1X to RADIUS, per-userWPA3 adds optional 192-bitWPA3-Personal (SAE)resists offline crackingWPA2-PSK only for legacyCoverage gapsor dead zones?YesRun a site survey, build a heat map, reposition APsHiding the SSID is not security; never use WEP or original WPA
Cheat sheet

Cheat sheet

  • Map each 802.11 standard to its Wi-Fi generation name
  • Memorize the band and top speed of each legacy 802.11 standard
  • 802.11ac (Wi-Fi 5) is 5 GHz only
  • The 6 GHz band is reachable only by Wi-Fi 6E and Wi-Fi 7
  • OFDMA is the defining efficiency feature of Wi-Fi 6
  • 2.4 GHz reaches farther; 5 and 6 GHz go faster with less interference
  • Only channels 1, 6, and 11 are non-overlapping in 2.4 GHz
  • Co-channel and adjacent-channel interference are different problems
  • Keep 2.4 GHz at 20 MHz; save wide channels for 5 and 6 GHz
  • 2.4 GHz shares spectrum with non-Wi-Fi devices
  • SSID is the network name; BSSID is the AP radio's MAC
  • Hiding the SSID is obscurity, not security
  • A BSS is one AP; an ESS is one SSID across many APs
  • Roaming needs overlapping cells and a clean channel plan
  • Infrastructure, ad-hoc, and mesh are the three WLAN topologies
  • WPA2 still uses AES in CCMP; its weakness is the PSK handshake
  • WPA3-Personal uses SAE to defeat offline password cracking
  • Personal uses one shared key; Enterprise authenticates each user via 802.1X
  • Know the 802.1X role triad: supplicant, authenticator, RADIUS server
  • Isolate a guest SSID from internal VLANs
  • Directional antennas focus a beam; omnidirectional cover an area
  • Run a site survey to plan AP placement and find dead zones
  • WEP's RC4 with a 24-bit IV lets attackers recover the key from captured traffic
  • WPA3 makes Protected Management Frames mandatory; WPA2 only made them optional
  • 802.1X enterprise: PEAP-MSCHAPv2 needs only a server cert; the AP needs a RADIUS shared secret

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References

  1. IEEE 802.11 Working Group (Wireless LAN standards) Whitepaper
  2. Wi-Fi Alliance Whitepaper
  3. Wi-Fi CERTIFIED 6 (and Wi-Fi 6E) Whitepaper
  4. Wi-Fi CERTIFIED 7 Whitepaper
  5. RFC 7664 — Dragonfly Key Exchange (basis of WPA3 SAE) Whitepaper
  6. IEEE 802.1X-2020 — Port-Based Network Access Control Whitepaper