RobotnixAcademy

Week 09 · lesson

Lesson 3: Read IP, Route, DNS, and Connectivity Evidence

Core path: 42 minutes

Today the commands are not magic spells. Each one answers a narrower question.

All output in this lesson is supplied or simulated. Do not probe the school network.

Interface configuration

Example Windows-style evidence:

IPv4 Address . . . : 192.168.40.25
Subnet Mask  . . . : 255.255.255.0
Default Gateway .  : 192.168.40.1

Question answered: did the endpoint receive/plausibly have the expected local IPv4 configuration?

Ping

ping 192.168.40.1

A reply supports reachability to that target under that test. A timeout does not identify the root cause by itself.

Traceroute / tracert

Path-hop output can show which routed hops respond along a path. Missing responses can be caused by filtering or device behavior, so do not treat every * as a dead router.

nslookup

nslookup portal.test

Question answered: does the queried DNS path return an answer for the name?

If direct-address communication works while name lookup fails, DNS becomes a stronger boundary.

APIPA comparison

Expected:

192.168.40.25/24
Gateway 192.168.40.1

Observed:

169.254.33.18/16
No gateway

That is strong evidence that expected IPv4 configuration was not obtained. It is not proof the NIC hardware is dead.

Student action

Annotate each simulated command with:

question:
observation:
what it supports:
what it does not prove:
next test:

Use at least ipconfig/ip, ping, traceroute/tracert, and nslookup.

Evidence checkpoint

The output matters only when you connect it to the architecture:

interface → local path → gateway → name/path → service

Screenshots without interpretation are not troubleshooting documentation.

System process animation

Packet to service: prove each boundary

Step through the technician test path from local link and addressing to gateway, name resolution, transport, and the application response.

Technician question: Which successful test proves only IP reachability, and which later test finally proves the application service?

Read it. Prove it.

Lesson knowledge checks

Answer from the lesson you just completed. Results stay in this browser and are not submitted.
Knowledge check 1

What information does `ip route` primarily provide on a Linux-like system?

Knowledge check 2

If `nslookup` fails but direct access to a known IP works, which service is the strongest suspect?