Ethernet cable (lesson)
developer:
create an ethernet extension cable for a computer to plug into the back of your house ethernet router.
qualifying statement
Learners will use techniques and tools to construct and test an ethernet cable. Learners will receive immediate feedback as to whether they have terminated the wires correctly, those that fail are required to redo the termination until it works. Sufficient length must be reserved on the cable to allow for mistakes otherwise the resulting cable might not be too useful.
example outcomes
- using measurements and common sense to arrive at sufficient cable length (taking into account that a termination may fail and need to be done again).
- use a terminating tool to cut and strip the cable without cutting themselves
- arrange the wires in accordance with the IEEE standard T-568-B
- terminate the wires on each end of the cable with an RJ45 connector
- test the cable with a cable tester
- rework the cable on failure
Required
- drum/box/length of cat5e or cat6 cable
- RJ45 connectors
- RJ45 crimp tool
- side-cutters
- patience, and a
- an RJ45 cable tester
How to
- measure the length of cable.
- lay the cable out
- cut the cable
- get the wires in the right order and insert into the RJ45 connector and crimp
- do the same for the other end.
- test with the cable tester
🚩 It is a bit tricky getting the cable cut and terminated; have your instructor guide you through the process.
🚩 The pinout for the connector is also tricky, the wires are colour-coded, but the white wires with colour traces are quite hard to see, and you may have difficulty distinguishing between the green and blue trace wires. Sometimes the orange wires look brown - so take care.
🚩 It is quite hard to see the trace wires in the connector, even though the connector is clear.
The later snap-connectors have a through hole/slot that the wires poke out of to make it easier to terminate. You will have better success with those types of connectors because they are easier to thread and the wire hangs out the slot so you can see if you got the wires in the right order before crimping the connector pins. The connector pins penetrate the wire insulation and make contact with the metal and the plastic sheath is held captive by a crimp area on the connector. There are two different termination tools for each type of connector.
☢ Note that the old style connector crimp tool is dangerous and has exposed cutting blades.
two types of termination tools |
 one with a through hole and the other without |
pinouts
There are standard pinouts for the RJ45 connector and standard wire colours; we are going to use the industry T-568B standard arrangement for a straight-through cable.
testing
The cable will be tested with a typical cable tester. The LEDs must light sequentially in order from 1 to 8. If there are any connections missing the LED will not light, and if you have wires swapped over they will not light in the correct order. The termination must be rejected in the failure cases.
Did you know that you can buy cables and connectors from:
- Bunnings, and
- Jaycar
You may also find made-up cables at:
- Jaycar
- Office Works
- JB HiFi
Made up cables and boxes of cables may be purchased from ebay - which is where I buy my boxes of cat5e/cat6 cable from (and wait).
using the cable
This cable is to be inserted into the router LAN[1] port and the other end can be inserted into the raspberry pi, or a laptop. It will provide slightly faster www access than using WiFi [2].
A before-and-after comparison will be done using ping to see how it performs.
- determine the IP address of your raspberry pi
ip addr
🚩 Note the interfaces such as physical network and wireless network interface device names.
- plug the ethernet cable into the router and into the raspberry pi and note the addresses again
ip addr
🚩 Note: the new interface is the wired interface.
🚩 Note: that each interface is assigned a physical MAC address.
🚩 Take a note of the IP address e.g. 192.168.0.7
Home routers usually reserve the 192.168.X.1 IP address where X is some number. Larger routers may be on a bigger subnet [3] e.g. 10.X.X.1
Trying pinging your own IP address and note the response times (terminate with Ctl C).
ping localhost
🚩 Edit the command below so the numbers match your router gateway address; then pinging the router gateway
ping 192.168.X.1
Use ping to local host, and then ping the gateway with the cable connected and again with the cable disconnected and record the results. Note the response time and record in the following table (press edit to update):
response times
| ping results | ||
|---|---|---|
| localhost | gateway wired |
gateway WiFi |
| TBA | TBA | TBA |
additional
You may explore what happens with the IP routes when the cable is plugged in and when it is not via the command:
ip route
IP routes are how a computer decides which interface your IP traffic uses to reach a gateway. A gateway[4] is a device that will route traffic out to other networks outside your Local Area Network (LAN)[1] e.g. to https://www.raspberrypi.org
- trying pinging an external host
ping https://www.raspberrypi.org
🚩 Note: the IP address.