Broken Netlabs

Hands-on Cisco networking practice in two flavours: troubleshooting broken production networks and building enterprise networks from scratch. Everything runs in Cisco Packet Tracer or, for the greenfield curriculum, any simulator you prefer.

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Troubleshooting Labs

Eight Cisco Packet Tracer networks, each deliberately broken. Your job is to find the faults, prove the cause, fix them properly and document what you did. They are built to feel like a real incident: no change log, a pile of tickets, and a network that worked until the weekend.

Start here

1. Install Cisco Packet Tracer.
2. Pick a lab folder from the table below. Start with the smallest if this is your first time.
3. Read that folder's README.md first. It gives you the story, the network layout, the logins and what is expected of you.
4. Open the .pkt file in Packet Tracer and work through WORKBOOK.md.

The labs

Lab	Folder	Size	Tickets
TechPeak Enterprise	TechPeak-Enterprise-Troubleshooting	42 devices, head office, two data centres and branches	16
Harbourline Campus	Harbourline-Campus-Troubleshooting	52 devices, main campus, remote campus, depot and data centre	20
Meridian General Hospital	Meridian-Hospital-Troubleshooting	49 devices, hospital, clinic and data centre, with segmentation and ACL policy	20
National Bank	NationalBank-Enterprise-Troubleshooting	59 devices, head office, branches, DMZ, firewall and DR	26
Brightway Retail	Brightway-Retail-WAN-Troubleshooting	~20+ devices, head office hub-and-spoke WAN to six retail stores	20
Cardinal Capital	Cardinal-Capital-Troubleshooting	~25+ devices, London HQ, New York office and data centre for an investment bank	20
Kestrel DataCentre	Kestrel-DataCentre-Troubleshooting	~20+ devices, tiered data centre with campus office and partner extranet	20
Northgate DR	Northgate-DR-Troubleshooting	~25+ devices, primary DC, disaster-recovery DC and operations office	20

Every lab folder contains:

• *.pkt: the broken network to open in Packet Tracer.
• README.md: the story, the network overview and what is expected of you.
• WORKBOOK.md: the tickets, the wireless step and a fix log template.

How to work a lab

• Treat it as an incident, not a puzzle. Start with what affects the most users.
• Prove the cause with show commands before you change anything, and keep the output.
• Fix the root cause with the smallest change. No workarounds such as extra static routes or removing ACLs.
• Verify after every fix and check you have not broken something else.
• Save with write memory on every device you change.
• Be patient. Routing, spanning-tree and EtherChannel can take two to five minutes to settle.
• Some blocks are deliberate policy, not faults. Each lab's README lists what must stay blocked.
• Some faults hide behind others, so a test that still fails after a fix may have a second cause.

Wireless

Packet Tracer cannot pre-connect wireless clients in these files, so each workbook has a short manual step (M5). Do it after the wired network works.

Keeping a record

For each ticket write down: symptom, device, commands used, root cause, fix and how you verified it. Employers and assessors value this evidence as much as the fix itself.

Good to know

• Open the .pkt straight from the folder. Do not edit the README or workbook files while you work; copy the fix log into your own notes.
• If you are stuck, step back to the bottom of the stack: link, VLAN, IP address and gateway, then routing, then policy.

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CCNA in 90 Days – Greenfield Build Curriculum

Located in ccna-in-90-greenfield/ccnain90/.

A 100-lab documentation-driven curriculum for building enterprise networks from scratch. No pre-baked configs are provided. You read the business scenario and technical requirements, plan addressing, build the topology in your preferred simulator, and verify your own work.

The labs are split into a core CCNA track (50 labs) and advanced ENCOR-aligned projects (50 labs).

Core CCNA Track (Labs 01–50)

Phase	Folder	Labs	Focus
Foundations	01-foundations	01–10	CLI navigation, device hardening, IPv4 subnetting (192.168.X.0/24), VLANs (10/20/99), default gateways
Switching	02-switching	11–20	Multi-switch campus designs, 802.1Q trunks, STP root selection, EtherChannel
Routing & WAN	03-routing-wan	21–35	Inter-VLAN routing, WAN point-to-point (10.255.X.0/30), OSPF single-area, dual-site convergence
Security & Optimisation	04-security-optimization	36–45	ACL design and placement, SSH hardening, syslog and monitoring, network segmentation
Advanced Design	05-advanced-design	46–50	Multi-site enterprise (10.X.0.0/24), route summarisation, dual-ISP failover, template-driven builds

Advanced Projects

Located in ccna-in-90-greenfield/ccnain90/advanced-projects/. These are larger, scenario-based exercises for learners ready to go beyond CCNA.

Domain	Folder	Labs	Focus
Architecture	01-architecture	01–08	Dual-stack IPv4/IPv6, high availability (FHRP, SSO), SD-WAN and SD-Access concepts, QoS
Virtualisation	02-virtualization	09–13	VRF segmentation, GRE and IPsec tunnelling, LISP/VXLAN overlay concepts
Infrastructure	03-infrastructure	14–28	Advanced L2/L3, OSPF/EIGRP/eBGP, wireless architecture, IP services (NTP, NAT/PAT, multicast)
Network Assurance	04-network-assurance	29–33	SPAN/RSPAN/ERSPAN, NetFlow, IP SLA, Cisco DNA Center workflows
Security	05-security	34–43	DHCP snooping, DAI, port security, AAA/802.1X, CoPP, infrastructure hardening
Automation	06-automation	44–50	Python scripting, RESTCONF/NETCONF, JSON/YANG, EEM applets, automation strategy

What each greenfield lab contains

Every lab folder provides engineering specifications rather than step-by-step instructions:

• README.md - scenario, business constraints, technical requirements, implementation checklist and verification commands.
• addressing-plan.md - subnet and gateway assignments following a consistent master blueprint.
• topology-description.md - device roles, link types and port-level mapping.
• failure-testing.md - structured failure scenarios to inject and recover from.
• expected-outcomes.md - success criteria and reflection prompts.

Simulator support

Unlike the troubleshooting labs which require Packet Tracer .pkt files, the greenfield curriculum is simulator-agnostic. Build in Cisco Packet Tracer, GNS3, EVE-NG, Cisco Modeling Labs (CML) or physical hardware.

How to use it

• Self-study: work labs in order for a structured 50-day or 90-day CCNA path. Read the README, build the topology using the addressing plan and topology description, then verify using the expected outcomes and failure testing guides.
• Instructors: treat each lab folder as a lesson module with built-in answer keys, break/fix exercises and student reflection prompts.
• Revision: re-use later-phase labs (30–50) and the advanced projects as capstone scenarios.

See the full curriculum guide in ccna-in-90-greenfield/ccnain90/README.md.

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Suggested Learning Paths

New to networking? Start with the greenfield foundations (Labs 01–10), then try TechPeak Enterprise as your first troubleshooting lab.

Preparing for CCNA? Work through the full greenfield core track (Labs 01–50), then tackle the troubleshooting labs in order of size to build triage discipline.

Already certified, want practice? Jump straight into National Bank, Cardinal Capital or Northgate DR for challenging incident simulations, or the advanced projects.

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Good luck.

• Olumayowa