These questions describe a network symptom and ask you to identify the root cause or the correct fix. They appear across all certification exams and reward systematic thinking over memorisation. The best candidates follow a consistent troubleshooting framework even under time pressure.
Start Scenario PracticeA network administrator is troubleshooting a switch that is experiencing high CPU utilization. The administrator suspects a switching loop. Which command should be used to verify whether Spanning Tree Protocol has blocked any ports to prevent a loop?
Explanation: Spanning Tree Protocol prevents loops by blocking redundant ports. When a loop is suspected, checking STP status is essential. The show spanning-tree command provides detailed information about port roles and states, including which ports are blocking. If STP is functioning correctly, it will have blocked ports to break the loop, though high CPU may still occur during topology changes.
Users on VLAN 20 report that they can reach servers on VLAN 30 but cannot reach any hosts on VLAN 40. The administrator confirms that inter-VLAN routing is configured on a Layer 3 switch with switched virtual interfaces for all three VLANs. Which action should the administrator take first to isolate the problem?
Explanation: Because routing between VLAN 20 and VLAN 30 already works, the Layer 3 switch is functioning as a router. The fault is specific to VLAN 40, so the logical first check is whether its switched virtual interface is up and correctly addressed. An SVI stays down when the VLAN has no active member ports or when the VLAN itself has not been created.
A network technician is troubleshooting intermittent connectivity to a server. The technician suspects a duplex mismatch on a switch port connected to the server. Which command should be used to check the duplex setting and error statistics on the switch port?
Explanation: A duplex mismatch often causes late collisions, FCS errors, and runts on the side configured for half-duplex. The show interfaces command provides duplex mode and error counters for a specific interface. By examining these statistics, the technician can confirm whether a mismatch exists and take corrective action, such as setting both sides to auto-negotiate or matching duplex settings manually.
A user is unable to reach 'cisco.com' in their web browser but can successfully ping the IP address '72.163.4.161'. Which network service is most likely failing or misconfigured?
Explanation: This scenario highlights the distinction between basic connectivity and name resolution. If a user can reach a destination by IP but not by name, the underlying network path is functional, but the translation service is broken. Diagnosing DNS issues is a daily task for technicians, as it is often the root cause of 'internet is down' complaints when the connection is actually active.
A network technician is troubleshooting a PC that cannot access internal network resources. Which TWO steps are recommended to verify if the PC is receiving a valid IP address?
Explanation: Verifying the IP configuration is essential when network access fails. Using 'ipconfig' allows the technician to see if the PC has a valid address, subnet mask, and gateway. Checking the DHCP server configuration ensures that the scope is not exhausted and that the client is actually communicating with the server. These two steps confirm if the layer 3 addressing is correct before moving on to more complex layer 2 or routing issues.
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Practice all Troubleshooting Scenario QuestionsThese questions describe a network symptom and ask you to identify the root cause or the correct fix. They appear across all certification exams and reward systematic thinking over memorisation. The best candidates follow a consistent troubleshooting framework even under time pressure. These appear throughout the 100-150 and require you to apply your knowledge, not just recall facts.
Cisco doesn't publish an exact breakdown, but scenario-based questions (especially exhibit and command-output formats) make up a significant portion of the 100-150. Practicing each scenario type ensures you're ready for any format.
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