FirstTry

Objective 1.4

200-301

Identify interface and cable issues (collisions, errors, mismatch duplex, and/or speed).

Objective 1.4 sits in Network Fundamentals, which carries 20% of the CCNA exam. The questions below are original, written from the official objective title above, and each explanation cites the Cisco page it rests on.

Objective title verbatim from the official objectives. Cisco exam page ↗

A worked example

Shown solved, with the whole explanation open: this is what every question here carries.

1-4Network Fundamentals

Users on this access port report intermittent connectivity and slow transfers.

Switch# show interfaces GigabitEthernet1/0/12GigabitEthernet1/0/12 is up, line protocol is up (connected)  Hardware is Gigabit Ethernet, address is 00a3.8e21.4c0c  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX     4193 input errors, 2871 CRC, 1102 frame, 0 overrun, 0 ignored     0 output errors, 0 collisions, 0 interface resets     0 babbles, 0 late collision, 0 deferred

What do the counters point to?

A duplex mismatch with the attached deviceCorrect · your answerCorrect. CRC and frame errors on a full-duplex port point at the far end running half.
An oversubscribed output queue on the uplinkQueue exhaustion shows as Total output drops or Xmit-Err, and this interface reports neither.
A VLAN mismatch between switch and hostFrames in the wrong broadcast domain still arrive intact. A VLAN fault does not corrupt the frame check sequence.
An MTU mismatch on the switched pathFrames past the MTU land in the giants counter, which is not incrementing anywhere in this output.

Correct.

Checked against cisco.com, August 2026

Concept

Layer 1 error counters only mean something read against the operating state of the port. Counts that are routine on a shared segment become evidence of a fault when the interface reports full-duplex, since full-duplex switches collision detection off entirely.

Why A

This port is running full-duplex, so the collision counter is inactive and reads zero as expected. It is still counting CRC and frame errors on input, and Cisco's counter table names exactly that pattern as the signature to chase: the far end is running half-duplex, senses the wire busy mid-frame, and truncates or corrupts frames the switch then discards.

Source

If the FCS, CRC, alignment, or runt counters increment, check for a duplex mismatch. Duplex mismatch is a situation where the switch operates at full-duplex and the connected device operates at half-duplex, or vice versa. The results of a duplex mismatch are extremely slow performance, intermittent connectivity, and loss of connection.

Cisco: Troubleshoot Switch Port and Interface Problems, checked August 2026
#duplex-mismatch#show-interfaces#error-counters

Now you: objective 1.4 questions

No account needed. The explanation opens when you answer.

Sample question 1 of 3

1-4Network Fundamentals

A half-duplex 10 Mb segment has been up for a week and a user reports slow file copies.

Router# show interface ethernet 0Ethernet0 is up, line protocol is up  Half-duplex, 10Mb/s  2058015 packets input, 233768993 bytes, 1 no buffer  Received 1880947 broadcasts, 0 runts, 0 giants, 1 throttles  0 input errors, 0 CRC, 0 frame, 0 overrun, 3 ignored  298036 packets output, 32280269 bytes, 0 underruns  0 output errors, 10 collisions, 0 interface resets  0 babbles, 0 late collision, 143 deferred

What do the collision and deferred values indicate?

Sample question 2 of 3

1-4Network Fundamentals

A server on this 100 Mb port is fed by traffic arriving on a gigabit uplink.

Switch# show interfaces FastEthernet0/24FastEthernet0/24 is up, line protocol is up (connected)  Full-duplex, 100Mb/s  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 184392  Output queue: 40/40 (size/max)     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored     0 output errors, 0 collisions, 0 interface resets

What explains the output drops?

Sample question 3 of 3

1-4Network Fundamentals

Two Ethernet devices come up at 1 Gbps full duplex with flow control, and nobody set either side. What produced that agreement?

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Read the sources

These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.

More objectives in Network Fundamentals