"I tested it and it was fine"
A technician says, "I tested the new branch. It was fine." A week later the manager cannot reach the file server.
What did the technician test? With which tool? What was the answer? Nobody wrote it down, so nobody knows.
By the end of this lesson
Note
I can record a test as annotated evidence, from the test to the next step.
Key words
| Word | What it means | Example |
|---|---|---|
| Network | computers and devices joined together so they can share data | |
| IP address | a number that names one device on a network | 10.0.3.2 |
| Router | a device that passes messages from one network to another | |
| Ping | a tool that sends a small message to an address and waits for a reply | |
| Traceroute | a tool that lists each router a message passes through | |
| Expected result | what should happen, written before the test | |
| Actual result | what really happened | |
| Annotation | a short note that explains a piece of evidence |
The cells students fill in are left blank in this preview.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
This is practice
Important
The real Task 2 gives you a file for the exam board's own simulator. The board also sets how you record evidence. There is no such simulator here. This lesson teaches the skill with real commands in a lab. Ask your teacher how your evidence must look.
The columns of test evidence
| Column | What you write | Example |
|---|---|---|
| Test | What you check | Can h1 reach h2? |
| Purpose | Why you check it | Staff at desk 1 must reach the file server |
| Tool and data | The tool and the addresses used | ping 10.0.3.2 from h1 |
| Expected result | What should happen | Replies, 0% loss |
| Actual result | What really happened | Net Unreachable from 10.0.1.1, 100% loss |
| Comparison | Do they match? | No: it failed |
| Next step | What you do now | Run traceroute to find where it stops |
The cells students fill in are left blank in this preview.
Run test 1: ping the far host
sudo ip netns exec h1 ping -c 2 -W 1 10.0.3.2A command for the lesson’s lab terminal. It is shown here and not run.
If it replies
Tip
In the fresh lab the routers only know their own networks, so this ping fails. If it replies, somebody has already added routes in your lab. The lab's README says netlab reset starts it again.
Run test 2: trace the path
sudo ip netns exec h1 traceroute -n -w 1 -m 4 10.0.3.2A command for the lesson’s lab terminal. It is shown here and not run.