Wireless Deployment and Troubleshooting Lab
Key Takeaways
- Wireless PBQs often combine coverage, channel planning, security mode, VLAN mapping, and interference symptoms.
- 2.4 GHz offers longer range but fewer non-overlapping channels than 5 GHz and 6 GHz.
- WPA3-Personal, WPA3-Enterprise, captive portals, and open networks solve different use cases.
- Poor roaming, low SNR, channel overlap, and wrong power levels can look like application problems.
- Wireless validation should include client tests from the affected area, not only controller status.
Wireless questions test more than knowing that Wi-Fi uses radio. You may need to place APs, select channels, map SSIDs to VLANs, choose an authentication method, and interpret symptoms such as low throughput or intermittent roaming.
Scenario
A two-floor office needs wireless for employees, guests, and warehouse scanners.
| SSID | Users | Security | VLAN | Notes |
|---|---|---|---|---|
| Corp | Managed laptops | WPA3-Enterprise or WPA2-Enterprise where compatibility requires it | 10 | RADIUS-backed authentication |
| Guest | Visitors | Captive portal or isolated guest access | 40 | Internet-only policy |
| Scanner | Handheld scanners | Strongest mode supported by devices | 50 | May require 2.4 GHz for range and device support |
Band and Channel Planning
| Band | Strength | Constraint | Use case |
|---|---|---|---|
| 2.4 GHz | Better range and wall penetration | Crowded; only channels 1, 6, and 11 are typically non-overlapping in many regions | Legacy clients, low-bandwidth IoT, scanners |
| 5 GHz | More channels and less congestion than 2.4 GHz | Shorter range than 2.4 GHz | Corporate laptops and higher density offices |
| 6 GHz | More clean spectrum for Wi-Fi 6E or Wi-Fi 7 clients | Shorter range and newer client requirement | High-density modern client areas |
In a PBQ, avoid placing neighboring 2.4 GHz APs on overlapping channels. For example, use 1, 6, and 11 patterns rather than channels 3, 4, and 5. On 5 GHz and 6 GHz, channel planning still matters, but there are more choices.
AP Placement Checks
| Design item | Good answer | Risky answer |
|---|---|---|
| Coverage | APs placed near user areas with overlap for roaming | APs hidden in closets behind metal racks |
| Power | Enough to cover cells without excessive overlap | Maximum power on every AP |
| Warehouse | Directional or planned APs where shelving blocks signal | One office AP expected to cover all aisles |
| Guest access | Separate SSID mapped to guest VLAN and firewall policy | Guest clients bridged into user VLAN |
| Management | AP management on management VLAN | AP management exposed to guest clients |
Maximum transmit power is not always best. If APs are too loud, clients may stay associated to a distant AP instead of roaming to a closer one. If AP power is too low, coverage gaps and retries increase.
Troubleshooting Matrix
| Symptom | Likely cause | First checks |
|---|---|---|
| Clients connect but cannot get IP addresses | VLAN mapping, DHCP, trunk allowed list | SSID-to-VLAN map, DHCP scope, AP uplink trunk |
| Strong signal but poor throughput | Co-channel interference, channel width, congestion | Channel utilization, retries, client count |
| Good near AP, bad in warehouse aisles | Obstruction or multipath | Survey results, AP placement, antenna type |
| Authentication failures for Corp SSID | RADIUS, certificate, time, wrong security mode | AAA logs, supplicant config, certificate validity |
| Guests reach internal systems | Firewall policy or wrong VLAN assignment | Guest VLAN, ACL, firewall logs |
Mini Lab Walkthrough
Complaint: Warehouse scanners disconnect at the far end of aisle 7. Laptops in the office work normally.
Evidence:
- Scanner RSSI is weak at the far end of aisle 7.
- Retries are high in that aisle.
- The nearest AP is mounted outside the warehouse office.
- Metal shelving blocks line of sight.
- The scanners support only 2.4 GHz and WPA2-Personal.
Reasonable fix:
- Add or reposition an AP for aisle coverage.
- Use a supported 2.4 GHz channel plan such as 1, 6, and 11.
- Set transmit power based on survey results rather than maximum everywhere.
- Keep the scanner SSID mapped to the scanner VLAN.
- Apply firewall rules that permit only required application, DNS, DHCP, and NTP traffic.
Common PBQ Traps
- Solving every wireless problem by increasing power.
- Mapping a secure SSID to the wrong VLAN.
- Choosing WPA3-only for legacy devices that cannot support it.
- Ignoring DHCP and trunk issues when clients associate but cannot get addresses.
- Using overlapping 2.4 GHz channels in adjacent cells.
- Forgetting that physical materials, antenna direction, and mounting location affect coverage.
Clients can associate to a guest SSID but receive no DHCP lease. Which area should be checked first?
Which 2.4 GHz channel set is commonly used to avoid overlap in many deployments?
Which evidence helps troubleshoot poor wireless performance? Select three.
Select all that apply