NAT Troubleshooting Capstone: Interface Role + ACL

Bundle lab · $29.99

Advanced CCNA NAT/PAT troubleshooting on a compact 5-node CML-Free topology. A pre-broken edge (R1) sits between a private LAN and an ISP transit. Learners diagnose why inside-to-outside traffic never translates: the NAT interface roles are incorrect and the ACL referenced by NAT does not match the actual inside subnet. Fix both independently to restore translations, then verify from hosts and with IOS show commands.

Learning objectives

• Differentiate NAT inside vs outside interface roles and why role reversal prevents translations
• Use show ip nat statistics and show ip nat translations to correlate hits, misses, and active mappings
• Interpret standard ACL match logic and verify hit counts for NAT source-selection lists
• Validate routing before NAT so return traffic has a path back to the translated address
• Troubleshoot multi-fault NAT failures methodically without guessing

Troubleshooting focus

• If pings from the inside host fail and the NAT table stays empty, confirm that traffic actually crosses from an 'ip nat inside' interface to an 'ip nat outside' interface.
• If NAT statistics show misses but no hits, verify that the ACL referenced by the NAT rule matches the real source IP range of the inside host.
• Ensure the edge router holds a working default route to the ISP and that the ISP segment can reach the router’s outside address.
• After changes, clear stale state if needed (translations age quickly, but you can trigger new flows to observe fresh hits).