Checking LAN connectivity from a router: Which three IOS commands are most useful for diagnosing local network issues among the following list? (1) show interfaces (2) show ip route (3) tracert (4) ping (5) dns lookups

Introduction / Context:
When LAN connectivity problems arise, Cisco IOS offers show and exec tools that validate interface status, routing, and active reachability. Selecting the right set accelerates troubleshooting and reduces downtime.

Given Data / Assumptions:

• Candidate commands: show interfaces, show ip route, tracert, ping, dns lookups.
• You are working from a Cisco router CLI.
• Objective: diagnose LAN link health and IP reachability.

Concept / Approach:
'show interfaces' verifies Layer 1/2 state, errors, and duplex/speed. 'show ip route' confirms Layer 3 networks known to the router. 'ping' tests end-to-end IP connectivity and can use extended options (source interface, repeat count). 'tracert' is a Windows command; IOS uses 'traceroute'. 'dns lookups' is not a standard troubleshooting command name (IOS uses 'ip domain-lookup' to enable/disable DNS resolution).

Step-by-Step Solution:

Verification / Alternative check:
Optionally run 'traceroute' (IOS spelling) to isolate the failing hop; use 'show arp' for L2/L3 bindings if ARP resolution is suspect.

Why Other Options Are Wrong:
2 and 5 / 3 and 5: 'dns lookups' is not a diagnostic command; 'tracert' is not the IOS keyword. None of the above: Incorrect because 1, 2, and 4 are highly effective on IOS.

Common Pitfalls:
Leaving DNS lookup enabled can cause typos to hang CLI while IOS attempts name resolution; disable with 'no ip domain-lookup' during troubleshooting.

Final Answer:
1 ,2 and 4