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200-301 · Question #1169

A technician receives a report of network slowness and the issue has been isolated to the interface FastEthemet0/13. What is the root cause of the issue? FastEthernet0/13 is up, line protocol is up Ha

The correct answer is C. physical errors. The interface output shows a reliability score of 250/255, indicating frequent physical errors or instability on the link, which is the root cause of the reported network slowness.

Submitted by daniela_cl· Mar 5, 2026Network Access

Question

A technician receives a report of network slowness and the issue has been isolated to the interface FastEthemet0/13. What is the root cause of the issue? FastEthernet0/13 is up, line protocol is up Hardware is Fast Ethernet, address is 0001.4d27.66cd (bia 0001.4d27.66cd) MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 250/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive not set Auto-duplex (Full) Auto Speed (100), 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 18:52:43, output 00:00:01, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 12000 bits/sec, 6 packets/sec 5 minute output rate 24000 bits/sec, 6 packets/sec 14488019 packets input, 2434163609 bytes Received 345348 broadcasts, 0 runts, 0 giants, 0 throttles 261028 input errors, 259429 CRC, 1599 frame, 0 overrun, 0 ignored 0 watchdog, 84207 multicast 0 input packets with dribble condition detected 19658279 packets output, 3529106068 bytes, 0 underruns 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out

Options

  • Alocal buffer overload
  • Berr-disabled port on the far end
  • Cphysical errors
  • Dduplicate IP addressing

How the community answered

(17 responses)
  • A
    35% (6)
  • B
    18% (3)
  • C
    41% (7)
  • D
    6% (1)

Why each option

The interface output shows a reliability score of 250/255, indicating frequent physical errors or instability on the link, which is the root cause of the reported network slowness.

Alocal buffer overload

The output shows "Output queue 0/40, 0 drops; input queue 0/75, 0 drops," which means there are no packets being dropped due to buffer overload on this interface.

Berr-disabled port on the far end

The interface status is "FastEthernet0/13 is up, line protocol is up," indicating the port is active and operational, not in an err-disabled state on either end.

Cphysical errorsCorrect

The `reliability 250/255` metric indicates that the interface has experienced a significant number of errors over the weighted average period, directly pointing to underlying physical errors such as bad cabling, a faulty transceiver, or an issue on the connected device's port, causing retransmissions and slowness.

Dduplicate IP addressing

Duplicate IP addressing typically manifests as intermittent connectivity issues or ARP conflicts, but it would not directly result in a low reliability score on a physical interface.

Concept tested: Interpreting 'show interface' output for troubleshooting

Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet-interface/10565-3.html

Topics

#Cisco show interface#Network troubleshooting#Physical layer errors#Interface errors

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