Resource Cheatsheet
A+ Core 1 2.8: Network Tools
Professor Messer A+ 220-1201 objective 2.8 — crimpers, Wi-Fi and spectrum analysers, tone generator and probe, punch-down tools, cable testers, loopback plugs, taps and SPAN.
- Updated
- Reading time
- 7 min read
- Detail
- A+ Core 1
- Detail
- Network Tools
On this page
In one line: crimpers and punch-down tools build the copper, cable testers and loopback plugs tell you whether the cable or the interface is at fault, tone generators find which cable is which, Wi-Fi and spectrum analysers make radio visible, and taps or port mirrors get you the packets.
Companion to: Professor Messer, CompTIA A+ 220-1201 Core 1, objective 2.8 (Network Tools). The full version is the Network Tools class notes; the section overview is the Section 2 sheet.
The toolbag at a glance
| Tool | Use it to | Key fact |
|---|---|---|
| Cable crimper | Fit a connector (usually RJ45) to copper | Contacts pierce the insulation; crimp also clamps the cable stay |
| Wi-Fi analyser | See channels, signal strength, interference, clients | 802.11 only |
| Spectrum analyser | See all radio energy in the band | Finds non-Wi-Fi interference |
| Tone generator + inductive probe | Find one cable among hundreds | Probe hears it without touching the copper |
| Punch-down tool | Terminate wires onto a punch-down block | Seats and trims in one push |
| Cable tester | Check pin 1→1, 2→2 … 8→8 | Continuity only, not quality |
| Loopback plug | Test one interface in isolation | Not a crossover cable |
| Physical tap | Copy traffic in line | Fibre taps often passive (no power) |
| Port mirror / SPAN | Copy a switch port’s frames to an analyser | No cabling change needed |
Crimping copper
| Item | Why |
|---|---|
| Crimper | Presses the connector on permanently |
| Snips / electrician’s scissors | Cut and square the wires |
| Wire stripper | Remove the jacket without nicking pairs |
| Cable tester | Prove it before you install it |
- Contacts are pointed and pierce each wire’s insulation — no stripping of individual wires.
- The crimp also presses a cable stay onto the jacket so a tug can’t pull the wires out.
- T568B: W-Or, Or, W-Gn, Bl, W-Bl, Gn, W-Br, Br — same standard at both ends for a patch cable.
- Untwist as little as possible (~13 mm max).
Wireless: which analyser?
| Symptom | Tool |
|---|---|
| Neighbouring SSID on my channel; weak signal; who’s connected | Wi-Fi analyser |
| Channel looks clear but performance is terrible | Spectrum analyser (microwave, cordless phone, Bluetooth, camera) |
Signal close to the noise floor = little headroom = poor throughput. The gap is the SNR.
Tracing a cable
- Clip the tone generator to the cable — RJ45, coax, or straight onto the punch-down block.
- Take the inductive probe to the other end; sweep the bundle in halves until it sings.
- Confirm end to end with a cable tester, then document the position.
Don’t tone a cable that’s still plugged into live equipment (PoE, phone lines).
Punch-down blocks
| Point | Detail |
|---|---|
| What | Where many cables land so cross-connects are short jumpers |
| Tool | Seats the wire, contacts cut the insulation, excess is trimmed — one push |
| Craft | Keep the twists right to the block; they cancel interference |
| Admin | Blocks are numbered — record which number goes where |
| Types | 66 (telephone) · 110 (data); blades differ, one edge cuts |
Cable tester vs loopback plug
| Cable tester | Loopback plug | |
|---|---|---|
| Tests | The cable | One interface |
| Finds | Opens, crossed pairs, shorts | A faulty NIC or port |
| How | Continuity, pin by pin, 1–8 | TX wired back into RX; interface in diagnostic mode |
| Doesn’t tell you | Bandwidth, crosstalk, attenuation (that’s a certifier) | Anything about the cable |
| Watch out | “Tests fine” ≠ good cable | Not a crossover cable |
RJ45 loopback: pin 1→3, 2→6. Serial (DB9) loopback: pin 2→3. Software loopback (127.0.0.1 / ::1) is a different idea entirely — it tests the stack, not the hardware.
Capturing traffic: tap vs SPAN
| Physical tap | Port mirror (SPAN) | |
|---|---|---|
| Install | Breaks the link — needs a window | Switch config change |
| Needs | Tap hardware; copper taps need power, fibre taps often passive | Managed switch |
| Fidelity | Everything on the wire, errors included | Can drop frames when the switch is busy |
| Also called | — | Port redirection, SPAN (Switched Port ANalyzer) |
Pick the tool
| Clue | Tool |
|---|---|
| No connector on the cable | Crimper |
| Which of these 200 cables is it? | Tone generator + inductive probe |
| Terminating onto a block in the comms room | Punch-down tool |
| Did I get the eight wires in the right order? | Cable tester |
| Is it the cable or the NIC? | Cable tester, then loopback plug |
| Clear channel, awful Wi-Fi | Spectrum analyser |
| Need every frame, nothing dropped | Physical tap |
| Need a capture without touching the cabling | Port mirror / SPAN |
🔐 Security notes
- A tap or a SPAN port is a wiretap: every unencrypted packet on that link — HTTP, Telnet, FTP, SNMP v1/v2c credentials included. Comms room access and switch admin access are equally sensitive.
- Mirroring needs no physical access, just a switch login. Management on its own VLAN, authenticated accounts, and log changes to mirror config.
- Passive fibre taps are undetectable from the network side — no power draw, no change in behaviour. Locked rooms and inspected cable paths are the control.
- An unused live wall socket is an open door: patch only what’s in use, disable unused ports, use 802.1X.
- Encryption survives a tap; obscurity doesn’t. HTTPS, SSH, LDAPS, SNMPv3.
- Same tools, blue team: a permanent tap or mirror port is how an IDS or network sensor gets fed.
Practice drills
1. How do RJ45 contacts connect to the copper?
The pointed contacts are driven through the insulation into the copper (insulation displacement). No stripping of individual wires.
2. Why do you need an inductive probe as well as a tone generator?
You can’t hear a tone travelling down copper. The probe picks it up inductively, without touching the conductor.
3. What two things does a punch-down tool do at once?
Seats the wire in the block and trims the excess.
4. A cable passes the tester but throughput is poor. What's the tester not telling you?
It’s a continuity test only — nothing about quality: length, crosstalk, attenuation, untwisted pairs. A certifier measures those.
5. Loopback plug vs crossover cable?
A loopback folds one interface’s TX back into its own RX for isolation testing; a crossover joins two different devices.
6. What does SPAN stand for, and when do you use it over a tap?
Switched Port ANalyzer. Use it when you can’t break the link — it needs only a config change on a managed switch.
7. Why are fibre taps often passive?
They split off a fraction of the light, so they need no power and can’t drop the link by losing it.
8. Clear Wi-Fi channel, terrible performance. Which tool?
A spectrum analyser — the interference isn’t 802.11 (microwave oven, cordless phone, camera).
Key takeaways
- Crimper and punch-down tool build copper; keep the twists and document the block numbers.
- Cable tester = continuity (opens, crossed pairs); loopback plug = one interface in isolation. Neither is the other.
- Tone generator + inductive probe find one cable among hundreds without touching the copper.
- Wi-Fi analyser sees 802.11; spectrum analyser sees everything else in the band.
- Tap = in-line, complete, breaks the link to fit; SPAN = switch-copied, no rewiring, can drop frames.