Wi-Fi, Cabling, Connectors, and Transceivers Quick Table
Key Takeaways
- Media questions ask you to match distance, bandwidth, connector, interference, and installation constraints—pick the medium that fits, not the newest.
- Cat 6a carries 10 Gbps to 100 meters; Cat 6 carries 10 Gbps only to about 55 meters; copper Ethernet is capped near 100 m total.
- Single-mode fiber (laser, ~9µm core) reaches tens of kilometers; multimode (LED/VCSEL, 50/62.5µm core) is for shorter campus runs.
- Transceivers must match speed, media (fiber vs copper), connector, wavelength, and distance—speed alone is never enough.
- Wi-Fi design depends on band (2.4/5/6 GHz), channel plan, security (prefer WPA3), antenna, transmit power, and client capability.
Media and Wireless Quick Tables
Physical-media items on N10-009 (Objectives 1.5 and 2.x) are practical. The stem hands you a distance, environment, speed, or connector constraint and asks for the medium that fits the requirement—not simply the highest-bandwidth option. Memorize the numbers below; distractors are usually a cable rated too short or a transceiver matched on speed alone.
Wi-Fi Quick Table
| Band | Range/density | Channel notes |
|---|---|---|
| 2.4 GHz | Longest range, most interference | Only 3 non-overlapping 20 MHz channels (1, 6, 11) |
| 5 GHz | Shorter range, higher density | Many channels; DFS channels avoid radar |
| 6 GHz | Shortest range, cleanest spectrum | Wi-Fi 6E/Wi-Fi 7 clients only |
Generation cheat sheet: Wi-Fi 4 (802.11n) 2.4/5 GHz; Wi-Fi 5 (802.11ac) 5 GHz; Wi-Fi 6 (802.11ax) 2.4/5 GHz; Wi-Fi 6E adds 6 GHz; Wi-Fi 7 (802.11be) adds 320 MHz channels and Multi-Link Operation. Prefer WPA3 where supported and 802.1X/enterprise authentication for managed corporate SSIDs. A captive portal handles guest sign-in but never replaces VLAN and firewall isolation. Good roaming needs cell overlap (~15–20%), matched power, and proper channel planning.
Copper Cabling
| Cable | Max speed / distance | Notes |
|---|---|---|
| Cat 5e | 1 Gbps to 100 m | Common installed base |
| Cat 6 | 10 Gbps to ~55 m, 1 Gbps to 100 m | Tighter spec than 5e |
| Cat 6a | 10 Gbps to 100 m | Standard for new 10G drops |
| Cat 7/Cat 8 | 10–40 Gbps (Cat 8 ~30 m) | Cat 8 for short data-center runs |
Use plenum-rated (CMP) cable in air-handling spaces where code requires it, shielded twisted pair (STP) in high-EMI areas (and bond/ground it), and RJ45 as the standard endpoint/patch connector. Coaxial (F-type connector) remains for cable broadband.
Fiber Cabling and Connectors
| Item | Best fit | Notes |
|---|---|---|
| Multimode (MMF) | Short building/campus links | 50/62.5µm core, LED/VCSEL, orange/aqua jacket |
| Single-mode (SMF) | Long links, tens of km | ~9µm core, laser, yellow jacket |
| LC connector | Modern small-form-factor | Common on SFP modules |
| SC connector | Larger push-pull | Older or higher-power |
| UPC polish | Low-loss, blue connector | Standard data use |
| APC polish | Angled, green connector | Lowest reflection; never mate to UPC |
Transceivers and Optics
| Item | What to match |
|---|---|
| SFP | Speed, media, connector, wavelength, distance |
| SFP+ | 10 Gbps links |
| QSFP/QSFP28 | 40/100 Gbps aggregation, data center |
| SX optics | Short multimode (850 nm) |
| LX/LR optics | Longer single-mode (1310 nm) |
| DAC | Short direct-attach copper, in-rack |
| AOC | Active optical cable, short high-speed |
Selection Scenarios
| Requirement | Likely answer |
|---|---|
| 10 Gbps to a desk within 100 m | Cat 6a with RJ45 |
| Building-to-building, electrical noise | Single-mode fiber |
| Switch uplink with LC patching | SFP+ optic, matching wavelength, LC |
| In-rack 10/25G between switches | DAC twinax cable |
| Guest Wi-Fi, Internet only | Guest SSID → guest VLAN → firewall policy |
Worked Scenario: Choosing a Closet Uplink
A wiring closet 220 meters from the core switch needs a 10 Gbps uplink. Cat 6a is immediately disqualified because copper Ethernet is capped at roughly 100 meters regardless of category. Multimode fiber with SR (short-reach, 850 nm) optics typically reaches about 300–400 meters at 10 Gbps over OM3/OM4, so it can work—but if the run is mixed with older OM1/OM2 the budget shrinks fast. The safe, exam-favored answer is single-mode fiber with LR (long-reach, 1310 nm) optics, which comfortably exceeds 10 km. The teaching point is that you reason from distance first, then media, then the matched optic and connector—never the reverse.
Reading a Wireless Survey
Wi-Fi troubleshooting items often hand you signal numbers. RSSI (received signal strength indicator) near −67 dBm is good for data and voice; weaker than about −75 dBm degrades throughput. SNR (signal-to-noise ratio) below ~20 dB means noise is competing with the signal, common near microwaves, Bluetooth, or dense neighboring WLANs on 2.4 GHz. Co-channel interference (cells sharing channel 1, 6, or 11) and adjacent-channel overlap both reduce airtime.
Before adding access points, confirm the channel plan, transmit power, and whether the client even supports the band you deployed—adding a 6 GHz access point does nothing for a Wi-Fi 5 laptop.
PoE Planning Note
Many access points, IP phones, and cameras draw power from the switch. PoE standards set budgets: 802.3af delivers ~15.4 W per port, 802.3at (PoE+) ~30 W, and 802.3bt (PoE++) up to ~60–90 W for pan-tilt cameras and Wi-Fi 6/7 access points. The exam tests whether a switch's total power budget supports all powered devices, not just per-port capacity—forty 30 W devices need a 1200 W budget the switch may not have. If an access point boots, then resets under load, suspect insufficient PoE class or an undersized power supply rather than the radio.
Always match the powered device's class to both the port standard and the switch's aggregate budget.
Common Traps
- Selecting copper for long outdoor building-to-building runs (distance and electrical risk).
- Mating APC to UPC connectors—the angled and flat polishes do not pair.
- Installing non-plenum cable in an air-handling plenum where code requires CMP.
- Choosing a transceiver by speed only and ignoring fiber type, connector, and wavelength.
- Deploying a guest SSID without VLAN and firewall isolation.
- Assuming 6 GHz helps clients that lack 6E/Wi-Fi 7 radios.
A building-to-building link must span 600 meters through an area with heavy electrical interference. Which medium fits best?
Which connector is commonly found on modern SFP and SFP+ fiber transceivers?
Which factors must be matched when selecting a fiber transceiver? Select three.
Select all that apply