Diagnosing Network Connectivity

What you will be able to do

• Explain the five core support decisions involved in diagnosing network connectivity.
• Choose a safe inspection or support method that matches a stated user need.
• Interpret the result as evidence before deciding whether to change system state.
• Apply an identify, inspect, act, verify, document, and recover workflow to a realistic support case.

01

Build the Support Map

Trace connectivity from physical link through adapter, IP configuration, gateway, DNS, and application endpoint.

Reliable support begins by separating the user's visible symptom from the system layers that could produce it. Record the affected user, exact device or service, timing, scope, expected behavior, observed behavior, and any recent change before proposing a cause.

Use read-only evidence first. Preserve the starting state, ask one focused question at a time, and compare an affected example with a known-good example whenever that comparison is safe and relevant. This creates a baseline another technician can review.

02

Physical link

Physical or wireless link evidence shows whether the device can communicate with its immediate network connection. In this lesson, it answers one specific support question. Record its evidence separately from the other layers instead of folding everything into a general guess.

Check cable, radio state, signal, port, and adapter status before changing IP settings. Start with this approved method: Inspect adapter status and one known-good path. Keep the target, time, user context, and visible result together so the reasoning remains reproducible.

The safety boundary is specific: A connected icon does not prove internet reachability. The expected result is also specific: The local connection path is confirmed or isolated. If the observation does not match that result, preserve it and return to diagnosis instead of adding unrelated changes.

03

IP configuration

An IP address, prefix, gateway, and DNS settings define how the host reaches local and remote destinations. In this lesson, it answers one specific support question. Record its evidence separately from the other layers instead of folding everything into a general guess.

Record the complete adapter configuration and compare it with the network's expected values. Start with this approved method: Run `ipconfig /all` read-only. Keep the target, time, user context, and visible result together so the reasoning remains reproducible.

The safety boundary is specific: Do not assign a guessed static address. The expected result is also specific: Missing, automatic, and expected addressing are distinguished. If the observation does not match that result, preserve it and return to diagnosis instead of adding unrelated changes.

04

Gateway reachability

The default gateway is the local router used for destinations outside the connected network. In this lesson, it answers one specific support question. Record its evidence separately from the other layers instead of folding everything into a general guess.

Confirm local address first, then test the configured gateway before testing a remote IP address. Start with this approved method: Compare gateway configuration and controlled reachability tests. Keep the target, time, user context, and visible result together so the reasoning remains reproducible.

The safety boundary is specific: A blocked echo reply does not alone prove failure. The expected result is also specific: Local routing is separated from wider reachability. If the observation does not match that result, preserve it and return to diagnosis instead of adding unrelated changes.

05

Name resolution

DNS translates service names into addresses and can fail while direct IP connectivity remains available. In this lesson, it answers one specific support question. Record its evidence separately from the other layers instead of folding everything into a general guess.

Compare a known name lookup with a controlled IP test and record the configured resolver. Start with this approved method: Run `nslookup <approved-name>`. Keep the target, time, user context, and visible result together so the reasoning remains reproducible.

The safety boundary is specific: Cached answers can hide a current DNS change. The expected result is also specific: Name resolution is isolated from basic IP reachability. If the observation does not match that result, preserve it and return to diagnosis instead of adding unrelated changes.

06

Application endpoint

A working network path does not prove that the intended application, port, proxy, or remote service is available. In this lesson, it answers one specific support question. Record its evidence separately from the other layers instead of folding everything into a general guess.

Test the exact approved endpoint and compare another client or service only after lower layers pass. Start with this approved method: Test the documented application URL or service. Keep the target, time, user context, and visible result together so the reasoning remains reproducible.

The safety boundary is specific: Disabling security controls is not a diagnostic shortcut. The expected result is also specific: Application reachability is evaluated at the correct endpoint. If the observation does not match that result, preserve it and return to diagnosis instead of adding unrelated changes.

07

Apply One Controlled Support Action

Before changing state, name the exact target, required authorization, expected result, user impact, and recovery or reversal path. Protect unsaved work and relevant data, then explain any interruption or privacy exposure to the user in plain language.

Make one narrow change and stop. If a prompt, error, identity, device, path, or result differs from the approved plan, do not improvise with broader access or several fixes. Capture the new evidence and reassess the system layer that produced it.

A successful button, command, or progress message only confirms that an operation ran. Repeat the original user workflow and compare it with the baseline to decide whether the support objective was actually met without a new side effect.

08

Verify, Document, and Handoff

Verification should test the original success condition and one safe boundary condition. Record what changed, what remained unchanged, who confirmed the result, and which temporary permissions, sessions, files, or tools were removed after the work.

Write the support record so another person can continue without repeating completed steps. Include exact evidence and outcomes, but remove passwords, tokens, private content, and any personal information that the support purpose does not require.

Escalate when the required authority, product support, safety procedure, privacy permission, recovery evidence, or diagnostic certainty is missing. A complete escalation packages the symptom, scope, evidence, actions, results, risk, and next decision rather than forwarding an empty ticket.

09

Recap Before Practice and Prove

Start with physical link. Check cable, radio state, signal, port, and adapter status before changing IP settings. The result to preserve is the local connection path is confirmed or isolated.

Keep ip configuration separate. Record the complete adapter configuration and compare it with the network's expected values. Respect this boundary: do not assign a guessed static address.

Use gateway reachability to narrow the case. Confirm local address first, then test the configured gateway before testing a remote IP address. Verify that local routing is separated from wider reachability.

Before a broader action, review name resolution. Compare a known name lookup with a controlled IP test and record the configured resolver. Stop if cached answers can hide a current dns change.

Finish with application endpoint. Test the exact approved endpoint and compare another client or service only after lower layers pass. Record the final evidence, user outcome, and any remaining escalation or recovery boundary.