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fast ethernet interface is up and down

hi all,

I have a switch connected to a router which is experiencing a problem it shows down down status from time to time. I've attached the output of the interface.

Cisco-H#sh int f0/9

FastEthernet0/9 is up, line protocol is up

Hardware is Fast Ethernet, address is 0002.b951.6289 (bia 0002.b951.6289)

Description: Link to HQIG1 router

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, 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 00:00:15, output 00:00:01, output hang never

Last clearing of "show interface" counters 4d11h

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

68026 packets input, 24525353 bytes

Received 7796 broadcasts, 0 runts, 0 giants, 0 throttles

205 input errors, 134 CRC, 71 frame, 0 overrun, 0 ignored

0 watchdog, 7201 multicast

0 input packets with dribble condition detected

1639076 packets output, 197683910 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out


Hall of Fame Super Silver

Re: fast ethernet interface is up and down


There is inconsistency in your question that makes it difficult to answer. The title of your post says interface up and down, but the text of your question says down and down, and the output that you posted shows up and up.

Perhaps if you clarify your question we might be able to find answers for it.

In general up and up is normal and good when you have correctly configured interfaces connected. Up and down indicates that keepalives are failing/there is no link and frequently is caused when there is no device connected to the interface. Down and down frequently reflects that there is a problem with the interface.