Networking Tools: Crimper, Stripper, Punchdown, Tester, Toner Probe, Loopback Plug, Wi-Fi Analyzer, and Tap
Unit 3: Network Configuration. Lesson 15 of 41 in APlus Academy Core 1.
A technician's network bag holds a small set of tools, and the exam asks which one fits a job. Learn each tool by the problem it solves.
Making cables
- Cable stripper: removes the outer jacket without nicking the wires inside. A nicked conductor is a future intermittent fault.
- Crimper: presses an RJ45 (or RJ11) plug onto the wire ends. Arrange the eight wires in T568A or T568B order, push them fully into the plug, crimp, and check that the jacket is inside the strain relief.
- Punchdown tool: seats each wire into a 110 punchdown block on a patch panel or the back of a keystone jack and trims the excess in one push. The color codes on the jack tell you where each wire goes. A 66 block is the older telephone version.
Testing cables
- Cable tester: plug both ends in and it lights each of the eight wires in turn. It finds opens (a wire not connected), shorts, crossed pairs, and split pairs, and tells you whether the cable is straight-through or crossover. It does not measure quality.
- Cable certifier: a more expensive tester that measures the cable against its category (Cat 6a and so on); required for new installations that must be warranted.
- Loopback plug: a plug wired to send the port's transmit pins back into its receive pins. Plug it into a NIC or a switch port and the port should show link and pass a self-test. It isolates a suspected bad port without any other equipment.
Finding cables
- Toner probe (tone generator and probe): clip the generator onto one end of a cable and wave the probe along the bundle or the patch panel; it squeals when it touches the right cable. This is how you find which of forty unlabeled cables in the closet goes to a jack.
Wireless and traffic
- Wi-Fi analyzer: an app or handheld that shows every network in range, its channel, its signal strength, and interference. Use it to pick a clear channel, find dead spots, place access points, and see a rogue access point.
- Network tap: a hardware device inserted into a link that copies all traffic to a monitoring port without disrupting the link, so a protocol analyzer can capture it. A managed switch's port mirroring does the same job in software.
Matching the tool to the complaint
- "Which cable in the closet goes to room 214?" Toner probe.
- "Is this port on the switch dead?" Loopback plug.
- "The new run to the conference room does not link." Cable tester (look for an open or a miswire).
- "Wireless is slow in the east wing." Wi-Fi analyzer.
- "Terminate the new runs on the patch panel." Punchdown tool.
- "Put an end on this cable." Stripper, then crimper.
Networking Tools: Crimper, Stripper, Punchdown, Tester, Toner Probe, Loopback Plug, Wi-Fi Analyzer, and Tap, explained slowly
Tools by the job they do
Every tool in the bag answers a specific question. Put the questions in a table and the tool follows.
question tool how it answers Is this cable wired correctly, and are all 8 wires intact? cable tester lights each wire in sequence; shows opens, shorts, miswires Does this cable meet its category rating? cable certifier measures attenuation, crosstalk, length; prints a report Which cable in this bundle goes to that jack? toner probe tone on one end, probe squeals on the other Is this NIC or switch port dead? loopback plug loops TX to RX; the port should show link and pass a test How do I put a plug on this cable? stripper, then crimper jacket off, wires in T568 order, crimp How do I terminate a run on the panel or a jack? punchdown tool seats and trims each wire into the 110 block Which channel is clear; where is the dead spot? Wi-Fi analyzer shows SSIDs, channels, signal strength, interference How do I capture traffic on this link without disrupting it? network tap copies traffic to a monitoring port
Making a cable end, step by step
- Strip about 2 to 3 cm of jacket with the stripper; check that no conductor is nicked.
- Untwist the pairs only as far as needed and arrange the eight wires in T568B order: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown (T568A swaps the orange and green pairs).
- Trim them straight and push them fully into the RJ45 plug so the copper reaches the front and the jacket sits under the strain relief.
- Crimp firmly.
- Test with a cable tester: all eight lights in order means straight-through; a pattern swap means crossover; a missing light means an open; two lights together means a short.
Excess untwisting is the hidden cause of a cable that "tests fine but drops at gigabit"; that is what a certifier catches and a basic tester does not.
Punching down
A patch panel port or a keystone jack has eight slots with color codes printed beside them for both A and B. Lay each wire in its slot, set the punchdown tool with the cutting edge facing the waste end, and push until it clicks; the blade seats the wire and trims the tail in one motion. A 110 block is the modern data block; 66 blocks are older telephone blocks. Use the same standard (A or B) at every point in a run.
The loopback trick
A loopback plug is a plug whose transmit pins are wired back to its receive pins (1 to 3 and 2 to 6 on an Ethernet plug). Insert it into a NIC and the link light comes on and the NIC's diagnostics pass if the port is good; the same on a switch port. It answers "is it the port or is it everything else?" without a second computer or a known-good cable. Fiber loopbacks do the same with a short fiber jumper.
Tone and probe in the closet
A closet has forty unlabeled cables. Clip the tone generator to the wall jack in the office (or a patch cable plugged into it), go to the closet, and sweep the probe over the punched-down cables; the loudest squeal is the one. Label it, then move on. The generator can also find a break: tone stops where the cable is cut.
Wi-Fi analyzer, what to look at
The screen shows every SSID, its channel, and its strength in dBm (closer to zero is stronger; -50 is excellent, -70 is fair, -80 is poor). Use it to choose a channel nobody else is on, to walk a floor and mark where the signal fades, to place a new access point, and to spot a rogue access point using the company SSID. It cannot see non-Wi-Fi interference such as a microwave oven; a spectrum analyzer does that.
Tap versus port mirror
A network tap is a passive hardware device spliced into a link; it sends a copy of every frame to a monitoring port and keeps working even if unpowered. It never drops packets and never changes the link. A managed switch can mirror a port in software instead (SPAN), which is free but can drop frames under load. Both feed a protocol analyzer such as a packet capture tool.
How the exam asks it
- "Which tool identifies which cable in a bundle connects to a specific office?" A toner probe.
- "Which tool tests whether a switch port is functional without another device?" A loopback plug.
- "Which tool attaches an RJ45 connector to a cable?" A crimper.
- "Which tool terminates cable onto a patch panel?" A punchdown tool.
- "Which tool shows nearby wireless networks and their channels?" A Wi-Fi analyzer.
- "Which tool verifies that all eight wires are connected correctly?" A cable tester.
- "Which device copies traffic for analysis without interrupting the link?" A network tap.
What to memorize
- Stripper, crimper, punchdown for making; tester, certifier, loopback for testing; toner probe for finding; Wi-Fi analyzer for radio; tap for capture.
- T568B order and that A swaps the orange and green pairs. Loopback: TX to RX. 110 block for data, 66 for old phones.