Jensen IT Notes
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Documented lab

Network Packet Tracer Labs

I built this series to move from reading network concepts to configuring and checking them in Cisco Packet Tracer.

Overview

Why I built it

Configure a small-business network in stages, then diagnose deliberate VLAN, gateway, trunk, and router-subinterface faults.

Lab environment

The repository contains six Packet Tracer labs with topology files, device configuration, screenshots, and verification commands.

What I configured

Basic office networks, VLAN segmentation, router-on-a-stick inter-VLAN routing, ACLs, subnet expansion, access ports, trunks, and router subinterfaces.

Topology and workflow

How the work is organized

  1. 1 Build a basic office topology and confirm local connectivity
  2. 2 Separate Sales, HR, IT, and Shared devices with VLANs
  3. 3 Add router-on-a-stick inter-VLAN routing and ACL practice
  4. 4 Open intentionally broken files, isolate each fault, correct it, and repeat the ping tests

Troubleshooting

Problem encountered

The troubleshooting lab deliberately breaks four things: a PC on the wrong VLAN, an incorrect default gateway, a router subinterface error, and a trunk misconfiguration.

Checks, findings and fixes

HR client assigned to the wrong VLAN

Problem
PC3 used an HR subnet address but could not communicate as expected with the rest of the network.
Check
Run show vlan brief and compare the PC3 access port with the VLAN plan.
Finding
The PC3 switch port was assigned to VLAN 10 instead of HR VLAN 20.
Fix
Configure Fa0/3 as an access port in VLAN 20.
Verification
Pings from PC1 to PC3 and from PC3 to the shared printer and server succeeded.

Incorrect default gateway on PC4

Problem
PC4 could not reach devices outside its own VLAN while the rest of the routed network still worked.
Check
Review PC4 with ipconfig and compare its address, mask, and gateway with the VLAN 30 addressing plan.
Finding
The default gateway did not match the VLAN 30 router subinterface.
Fix
Set the PC4 gateway to 192.168.30.1.
Verification
PC4 reached PC3, Printer1, and Server1 after the correction.

Resolution

I used ping, show vlan brief, show interfaces trunk, and show ip interface brief to locate each fault, corrected the relevant port or Layer 3 setting, and repeated the connectivity tests.

Verification

  • show vlan brief confirmed access-port membership
  • show interfaces trunk confirmed the switch-to-router trunk
  • show ip interface brief confirmed router subinterface state and addressing
  • Post-fix pings reached the intended clients, printer, and server across VLANs

What I learned

A failed ping is only a starting point. Checking VLAN membership, trunks, gateways, and subinterfaces in order makes the fault easier to isolate.

GitHub repository

The repository contains the complete lab documentation, configuration notes, verification steps, and original screenshots.

View the complete lab and screenshots on GitHub