Learn · Practise · Troubleshoot

Learn networking by doing, not memorising.

Build a clear foundation, practise on Cisco labs, and use real troubleshooting workflows. Every topic starts in simple English and ends with something useful you can do.

Build my learning path Solve a network problem

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Beginner-friendly explanations
Practical engineer workflows

Learning boardStart here

What do you want to achieve?

Choose the result you need. We will point you to the shortest useful path.

01Learn from the beginningConcept → example → practice 02Prepare for a testFind gaps and revise 03Troubleshoot an issueSymptom → evidence → fix 04Use a quick toolCalculate and verify

UnderstandPlain-English concepts

See itExamples and commands

Try itGuided protocol labs

Prove itTools and practice tests

Choose by goal

Start with what you need today

Networking is easier when the resource matches the job. Pick a goal instead of searching through a long list.

I am learning

Build strong fundamentals

Start with addresses, switching, routing and verification in a sensible order.

Choose a learning path

I am revising

Find and close knowledge gaps

Use short tests to discover weak topics, then return to the matching guide or lab.

Browse practice tests

I am troubleshooting

Turn a symptom into evidence

Follow a safe check order for connectivity, routing, DNS, HTTPS and switching issues.

Open practical playbooks

I need a reference

Keep commands close at hand

Download subnetting, Cisco IOS and routing references for fast field use.

Get cheat sheets

Adaptive learning path

Tell us where you are starting

Select the option that sounds most like you. The learning board will change its recommended sequence, so you can focus on the next useful step.

Good learning rule: read until the idea is clear, practise until the output makes sense, then explain it without notes.

Beginner path

Build the map before learning the routes

3 focused sessions

01
UnderstandIP addresses and subnets
Learn what the address, mask, network and default gateway each tell you.
Open subnet calculator →
02
ConnectSwitching and local delivery
See how VLANs, MAC addresses and trunks move frames inside a network.
Practise switching →
03
RouteMove between networks
Compare static routes and dynamic routing, then inspect a routing table.
Start the OSPF path →

Practical explanation approach

Troubleshoot from symptom to proof

Do not jump straight to configuration changes. Use the same five questions for almost every network issue.

01
Define the symptom
Write what fails, who is affected, and when it started. “The internet is down” becomes “VLAN 20 users cannot open external websites since 10:15.”
02
Check the local facts
Verify link state, IP address, mask, gateway and VLAN. Bad local information can look like a routing or DNS problem.
03
Test one layer at a time
Try the gateway, a remote IP, then a hostname. Each result removes possibilities and tells you where to look next.
04
Compare expected and actual
Check routes, ARP, MAC tables, DNS answers, policies or certificates. Ask which output is different from the design.
05
Change, verify, record
Make one controlled change. Repeat the same test, confirm the result, and record what solved the problem.

Reachability

“I cannot reach the server”

Check: local IP → gateway → route → remote port.

Why: each test separates a host problem from a path or service problem.

Check reachability Trace the path

Name resolution

“The IP works, but the name does not”

Check: requested name → returned record → resolver → authoritative answer.

Why: working IP connectivity with a failing name usually points to DNS, not routing.

Inspect DNS records Use DNS checklist

HTTPS

“The site opens with a certificate warning”

Check: hostname → expiry → issuer → chain → system time.

Why: a valid date alone does not prove the certificate matches or is trusted.

Check live TLS Decode a certificate

Switching

“Devices in one VLAN cannot connect”

Check: access VLAN → trunk allowance → STP state → MAC learning.

Why: the frame must enter the right VLAN and have a forwarding path across every switch.

VLAN commands Test your knowledge

Save for later

Field-ready cheat sheets

Short references for revision, lab notes and live troubleshooting. Use them as prompts—not as a replacement for understanding the output.

Featured visual guide

IPv4 Subnetting Cheat Sheet

Use the CIDR table to recall mask and host values, then follow the block-size method to find the network, broadcast and usable range.

CIDR and dotted-decimal masks
Usable host counts and block sizes
Wildcard masks and private ranges

Download TXT Open full image Practise with calculator →

Cisco IOS

Troubleshooting commands

Show, debug, routing, switching and operational commands with a practical check order.

Download TXT

Routing

Protocol comparison

Compare RIP, EIGRP, OSPF and BGP by metric, scope, use case and verification method.

Download TXT

Command library

Find the right evidence faster

Each reference explains what to inspect—not only which command to type.

IOS

Cisco IOS

Show commands

Interfaces, errors, routes, ARP, MAC table, logs, CPU, memory and neighbours.

Open reference →

RTE

Routing

OSPF and BGP

Neighbour state, LSDB, prefixes, next hop, advertisements and routing policy.

Start with OSPF →

Switching

VLAN, trunk and STP

Access VLANs, native VLAN, MAC learning, root bridge, blocked ports and loops.

Open switching guide →

LIN

Linux and packets

Linux and tcpdump

Addresses, routes, sockets, DNS, neighbours, traffic filters and PCAP files.

Start with Linux →

SEC

Security

Firewall checklist

Policy, NAT, route lookup, sessions, VPN selectors, MTU, logs and packet proof.

Open checklist →

WEB

DNS and TLS

DNS and SSL

Authoritative answers, reverse DNS, expiry, SAN, issuer, chain and SNI checks.

Start with DNS →

CCNA

Study notes

CCNA notes library

Open the on-site CCNA note collection and continue into the topic you need to review.

Browse CCNA notes →

Verify, do not guess

Use a tool to check your understanding

A calculator or checker is most useful when you can predict the answer first. Make a prediction, run the tool, then explain any difference.

Browse all networking tools

Guided practice

Turn protocol theory into visible behaviour

Choose one protocol. Read the overview, build the configuration, verify the result, then intentionally break one thing and troubleshoot it.

Best first dynamic protocol

OSPF learning path

Neighbours, areas, LSAs, cost, DR/BDR, filtering and repair.

Start OSPF → 02

Cisco routing

EIGRP learning path

DUAL, successors, metrics, K-values, packets and repair.

Start EIGRP → 03

Inter-domain routing

BGP learning path

Peering, path attributes, routing policy and troubleshooting.

Start BGP → 04

Simple distance vector

RIP learning path

Operation, versions, timers, authentication and repair.

Start RIP →

Common questions

How to get more from this library

Small changes in how you study can make technical knowledge much easier to recall during an exam or real incident.

Where should a complete beginner start?

Begin with IPv4 addresses and subnet masks, then learn local switching and VLANs, and only then move to routing. Use the “New to networking” path above; it follows that dependency order.

Should I read a guide or start a lab first?

Read enough to predict what should happen, then start the lab. After each command, inspect the output and explain what changed. This is more effective than reading the full topic before touching a device.

How should I use the practice tests?

Take a short test before revision. Group wrong answers by topic, review only those topics, and repeat with a new test. The score matters less than understanding why each wrong option is wrong.

Can I use these resources during real troubleshooting?

Yes. Start with the five-step evidence workflow and use the relevant checklist or tool. Test only systems you own or are authorised to assess, and record the before-and-after result of every change.

One useful habit

Learn one concept. Verify one output. Explain it simply.

That short loop turns a reference page into knowledge you can use under pressure.

Choose your next lesson