Jeremy’s IT Lab - CCNA Troubleshooting Lab

Introduction

• Free CCNA Course: Follow along by subscribing, liking, commenting, and sharing.
• Lab Focus: Troubleshooting network misconfigurations to enhance CCNA skills. Misconfigurations in routers causing PC1 and PC2 to not communicate.

Lab Overview

• Network Topology: Same as previous lab but with intentional misconfigurations.
• Purpose: Practice identifying and fixing router misconfigurations.
• Recommendation: Attempt the lab individually to improve troubleshooting skills.

Problem Confirmation

• Initial Test: PC1 unable to ping PC2 (IP: 192.168.3.1).
• PC Configuration Check: Use IPCONFIG to confirm settings (IP, subnet mask, default gateway).
• Gateway Test: Successfully ping the default gateway (192.168.1.254).

Troubleshooting Steps

Router R1

• Check Interface Configurations: SHOW IP INTERFACE BRIEF confirms interfaces are UP/UP.
• Routing Table Analysis: SHOW IP ROUTE reveals a misconfigured static route.
  • Incorrect next-hop IP (192.168.12.3) should be 192.168.12.2.
• Fix: Remove incorrect route, add the correct one using the global config mode.
  • Commands: CONFIGURE TERMINAL, modify route and verify with DO SHOW IP ROUTE.

Router R2

• Interface Check: SHOW IP INTERFACE BRIEF finds no issues, interfaces are UP/UP.
• Routing Table Issue: Incorrect exit interface for 192.168.3.0/24 network (uses G0/0 instead of G0/1).
  • Initially adding correct route results in load-balancing.
• Resolution: Remove incorrect route to prevent load-balancing.
  • Commands: CONFIGURE TERMINAL, remove route and verify via DO SHOW IP ROUTE.

Router R3

• Interface Misconfiguration: SHOW IP INTERFACE BRIEF shows incorrect IP on G0/0.
  • Should be 192.168.13.3, not 192.168.23.3.
• Fix: Directly overwrite IP address—no need to remove first.
  • Commands: CONFIGURE TERMINAL, set correct IP.
• Routing Table Check: Verify static route to 192.168.1.0/24 via 192.168.13.2.

Final Verification

• Ping Test: Retry ping from PC1 to PC2 (192.168.3.1).
  • Initial failure expected, subsequent pings succeed.

Conclusion

• Result: Successful communication established between PC1 and PC2 after fixing router issues.
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