These questions present the output of IOS show commands — show ip route, show interfaces, show ip ospf neighbor, show vlan brief — and ask you to interpret what they reveal about the network state. Reading IOS output accurately is one of the highest-value skills on the CCNA.
Start Scenario PracticeWhich TWO statements correctly describe the causes or implications of CRC errors, runts, giants, or output errors as seen in the output of 'show interface' or 'show interface status'?
Explanation: Option B is correct because runts—frames smaller than 64 bytes—often result from collisions truncating frames on half-duplex links or a faulty NIC. Option D is correct because duplex mismatch can cause late collisions, which appear as output errors in 'show interface'; a device on one side full-duplex and the other half-duplex leads to collisions and framing errors. Option A is wrong because CRC errors can stem from faulty cabling, interference, or a mismatched NIC, not exclusively a bad switch port. Option C is wrong because giants (frames over maximum MTU) may be forwarded if the interface is configured with jumbo frames or the switch is set to accept oversize frames. Option E is wrong because 'show controllers' displays frame-size errors like runts and giants, including details beyond CRC errors.
Exhibit: OSPF neighbors are not reaching FULL state on an Ethernet segment with multiple routers. The output of show ip ospf neighbor on R2 shows a neighbor in the 2WAY/DROTHER state. What is the most likely reason?
Explanation: On a broadcast Ethernet network, two routers normally become fully adjacent through the DR or BDR. If the local router is stuck in 2WAY with another DROTHER, that is normal behavior. It is not a fault by itself.
You are connected to R1. The link between R1 and R2 is down. The output of 'show interfaces gigabitEthernet0/0' on R1 shows: 'GigabitEthernet0/0 is administratively down, line protocol is down (disabled)', with IP address 203.0.113.1/30, MTU 1500, and no input/output errors. Determine the root cause and configure the necessary fix to bring the interface up and restore connectivity.
Explanation: The interface status 'administratively down' means the interface was manually shut down using the 'shutdown' command. To bring it up, you must enter interface configuration mode and issue 'no shutdown', which administratively enables the interface. The other options are incorrect: setting speed to 100 Mbps or forcing full-duplex will not fix an administratively down state, and disabling keepalives is unrelated to the interface being disabled.
You are connected to SW1. The current configurations of interfaces GigabitEthernet0/1 and GigabitEthernet0/2 are as follows: Gi0/1: speed 100, duplex half, switchport access vlan 10 Gi0/2: speed 1000, duplex full, switchport access vlan 20 The port-channel interface 1 does not exist. Configure a LACP EtherChannel between SW1 and SW2 using these two interfaces, with port-channel 1 and mode active on both sides. Ensure the channel forms by resolving any speed/duplex or VLAN mismatches. After configuration, verify with 'show etherchannel summary'.
Explanation: The EtherChannel fails because member interfaces have mismatched speed/duplex (Gi0/1 is 100/half, Gi0/2 is 1000/full) and different VLANs (VLAN 10 vs 20). Additionally, the port-channel interface and physical interfaces must have matching VLAN assignments. To fix, unify both physical interfaces to the same speed (1000), duplex (full), and access VLAN (10). Then set channel-group mode active on each physical interface. Finally, ensure the port-channel interface also uses VLAN 10. Verify with 'show etherchannel summary' which should show the port-channel as SU (in use).
A network administrator notices that hosts in VLAN 10 cannot ping the default gateway (192.168.10.1). The switch's SVI for VLAN 10 is configured and the output of the show ip interface brief command shows its status as up/up. An embedded packet capture is configured. The exhibit shows ARP requests from a host to 192.168.10.1 but no ARP reply. Based on the exhibit, what is the most likely cause of the connectivity issue?
Explanation: The correct answer is B because the packet capture shows ARP requests from the host but no reply, indicating the switch's VLAN 10 SVI is not receiving the ARP frames. Since the SVI is confirmed up/up, the most likely cause is that the switchport connecting the host is not assigned to VLAN 10, causing the frames to be on a different VLAN. Option A is incorrect because the host's default gateway is correctly set to 192.168.10.1 (the SVI's IP); ARP requests are being sent but not answered. Option C is wrong because an ACL on the SVI would not block ARP (ARP is a Layer 2 protocol not filtered by IP ACLs), and the capture would show a reply if the SVI received the request. Option D is incorrect because the exhibit shows the SVI is up/up, ruling out an administratively down condition.
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Practice all Show Command Output QuestionsThese questions present the output of IOS show commands — show ip route, show interfaces, show ip ospf neighbor, show vlan brief — and ask you to interpret what they reveal about the network state. Reading IOS output accurately is one of the highest-value skills on the CCNA. These appear throughout the 200-301 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 200-301. Practicing each scenario type ensures you're ready for any format.
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