Wireless Fundamentals

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Plain-English explanation

Wi-Fi is Layer 2 wireless Ethernet (802.11). Clients associate to an access point using an SSID (network name). Each radio has a BSSID (AP MAC). 2.4 GHz has three non-overlapping channels (1, 6, 11 in North America); 5 GHz offers more channels and less interference but shorter range.

RF is shared media — distance, walls, interference, and power all affect SNR and throughput.

Deep dive

Wireless LAN components — AP, WLC, and client roles.
Supplementary figure from Panagiss CCNAmd

POE Classes — PoE power classes for APs and IP phones.
From study charts · jdepew88 CCNA notes

Additional topic reference

Wireless Networks — Panagiss CCNAmd notes

802.11 standards (awareness): 802.11n/ac/ax — CCNA focuses concepts not deep PHY. Know 2.4 vs 5 GHz tradeoffs.

| Band | Pros | Cons | |------|------|------| | 2.4 GHz | Range, penetration | Congested, fewer channels | | 5 GHz | Speed, more channels | Shorter range, more APs needed |

Association steps (simplified): Probe → Authenticate → Associate → (4-way handshake if WPA2/3).

AP modes: Autonomous (standalone), lightweight (CAPWAP to WLC), mesh — next lesson covers WLC detail.

CSMA/CA: Wireless uses collision avoidance (listen before talk) — hidden node problem motivates RTS/CTS (awareness).

Step-by-step — 2.4 GHz channel plan

Three APs in open office:

AP1 → channel 1
AP2 → channel 6
AP3 → channel 11

Avoid 1-2-3 overlap pattern — channels overlap in 2.4 GHz. Use the wireless channel planner tool in the next lesson.

Commands to know

Autonomous AP — basic WLAN (conceptual)

dot11 ssid CORP-WIFI vlan 10 authentication open ! interface Dot11Radio0 ssid CORP-WIFI channel 11

Verify on WLC/AP

show wlan summary show ap summary

Troubleshooting

| Symptom | Check | |---------|-------| | Slow Wi-Fi | Co-channel interference, wrong channel width | | Can't see SSID | AP down, wrong band, max clients | | Connects no IP | VLAN mapping, DHCP, gateway | | Random drops | RF noise, power save, roaming |

Wi-Fi issues are often VLAN/DHCP, not "magic RF."

Exam relevance

Exam trap

Channels 1, 6, and 11 are non-overlapping in 2.4 GHz — channel 3 overlaps both 1 and 6.

BSSID vs SSID

Multiple APs can share one SSID (same name) but each radio BSSID is unique.

Practice checklist

Draw 2.4 GHz channel overlap diagram for channels 1–11
Explain 2.4 vs 5 GHz choice for warehouse vs office
List association steps from client perspective
Identify SSID vs BSSID in a Wi-Fi scanner app
Preview WLC architecture in next lesson

Which 2.4 GHz channels are commonly non-overlapping in North America?

What does SSID identify?

Learning objectives