Wireless
Wireless LAN Fundamentals
Covers RF basics, access point modes, and the controller-based architecture used to deploy and manage enterprise WLANs. Focuses on how a WLC and lightweight APs work together using CAPWAP.
What you need to know
- 2.4 GHz has 11 usable channels in North America but only channels 1, 6, and 11 are non-overlapping.
- 5 GHz offers many more non-overlapping 20 MHz channels and less interference, but shorter range than 2.4 GHz.
- Autonomous APs run a full standalone IOS configuration; lightweight APs depend on a Wireless LAN Controller (WLC) for control-plane functions.
- Split-MAC architecture divides functions between AP and WLC: the AP handles real-time functions (beacons, MAC layer encryption) and the WLC handles management functions (authentication, mobility, RF management).
- CAPWAP (Control And Provisioning of Wireless Access Points) tunnels control traffic on UDP 5246 and data traffic on UDP 5247 between AP and WLC.
- A WLAN (SSID) is mapped to a VLAN/interface on the WLC; multiple SSIDs can share the same AP radio.
- Common AP deployment modes include local (normal client access), monitor (RF/IDS scanning only), sniffer, rogue detector, and FlexConnect for branch sites with a WAN link to the WLC.
Configuration commands
| Command | Mode | Purpose |
|---|---|---|
| show controllers dot11radio 0 | exec | Display radio interface status on an autonomous AP. |
| interface dot11radio 0 | config | Enter configuration for the 2.4 GHz radio interface on an autonomous AP. |
| ssid <name> | config-if | Create or select an SSID under the radio interface (autonomous AP). |
| channel <number|auto> | config-if | Set or auto-select the RF channel for the radio. |
| WLANs > Create New | gui | Create a new WLAN (SSID) on the WLC and assign a profile name. |
| WLANs > General > Interface/Interface Group | gui | Map the WLAN to a VLAN interface on the WLC. |
| Wireless > Access Points > AP Name | gui | View or change AP mode (local, monitor, sniffer, FlexConnect). |
| Controller > Interfaces > New | gui | Create a dynamic interface on the WLC bound to a VLAN for client traffic. |
| show ap summary | exec | List APs joined to the WLC (CLI on WLC). |
Verify it
- show ap summary
- show wlan summary
- show controllers dot11radio 0
- show cdp neighbors
- show interface dot11radio 0
Common mistakes
- Choosing overlapping 2.4 GHz channels (e.g. 1, 4, 8) instead of the non-overlapping 1/6/11 set, causing co-channel interference.
- Forgetting to map the WLAN to the correct dynamic interface/VLAN on the WLC, leaving clients unable to reach the right subnet.
- Leaving a WLAN disabled or not enabling broadcast of the SSID needed for the lab.
- Confusing autonomous AP CLI configuration with lightweight AP GUI/WLC configuration.
- Not verifying the AP has joined the WLC (CAPWAP state) before troubleshooting client issues.
Practise Wireless LAN Fundamentals in a real CLI
Generated labs, graded against the simulated network state.