Network Diagnostics & Troubleshooting Lab
Hands-on network analysis lab diagnosing TCP/IP connectivity, DNS failures, DHCP exhaustion, and packet-level inspection with Wireshark.
Overview
This lab models common enterprise network connectivity, latency, and addressing challenges. Traffic between clients, gateways, and servers was captured and inspected using Wireshark to analyze TCP 3-way handshakes, ARP resolutions, and DNS query flows.
Project Objective & Scope
To systematically diagnose OSI Layer 1 through Layer 4 network issues, pinpoint transmission anomalies with Wireshark filters, and validate subnetting designs.
Lab Environment & Hardware/Software
Implementation & Configuration Steps
1. Subnetting & Network Topology Design
Calculated /24 and /28 subnets using CIDR notation, allocating appropriate IP blocks and default gateways.
2. DHCP Scope & Options Configuration
Configured DHCP scopes with lease timers, Gateway (Option 3), and Domain DNS (Option 6).
3. Packet Inspection with Wireshark
Captured and analyzed the 4-step DHCP DORA process and standard TCP 3-way handshake sessions.
4. Incident Simulation & Resolution
Simulated IP collisions, incorrect subnet masks, and DNS misconfigurations to practice structured troubleshooting.
Troubleshooting & Problems Encountered
Clients could ping servers by IP address but failed to reach them via FQDN.
Ping to IP succeeded, whereas ping to hostname failed with "Host unreachable / not found".
Discovered an outdated DNS server IP inside DHCP Option 6. Corrected the DHCP scope and renewed client leases.
What I Learned & Key Takeaways
- Adopted a bottom-up OSI model troubleshooting methodology (Physical to Application layer).
- Mastered practical Wireshark capture and display filters to detect packet anomalies.