QuestionQ1387

Network Fundamentals

A technician receives a report of network slowness, and the issue has been isolated to interface FastEthernet0/13. 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

  • A local buffer overload
  • B err-disabled port on the far end
  • C physical errors
  • D duplicate IP addressing
Explanation

Large numbers of input errors—especially CRC and frame errors—indicate corrupted Ethernet frames arriving on the interface, which is characteristic of a physical-layer problem such as faulty cabling, interference, bad connectors, or failing hardware. The interface is up/up, so a far-end err-disabled condition is not supported, and there are no queue drops, overruns, or ignored packets to suggest local buffer overload.

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