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Switch port just shuts down by itself

Cisco 3750G switches, with high FCS errors.  I've been having a problem where a link between two switches just dies, and sometimes, it comes back by itself, maybe 30 min or an hour later.  Most of the time, I have to manually move the cable to another port, to get it to come back up, even a reboot of the switch doesn't do the trick.
I have already replaced one of the switches, but the problem persists. I have looked at the logs, and nothing there stands out, most of the errors just state the port went down or came back up.  I started looking at the fcs errors, and I noticed that especially on one switch, it's a really high number.
I have attached the screenshots, any idea's what can be causing this?  I would like to replace the cable, but I don't have another cable and it's a large task to install another one., as the distance traverses a different building. I am not using port security.  Both sides of the link are trunk ports.

I tried to clear the counters and controllers, but the commands I have tried are not working.   Any ideas what could be causing the high fcs errors and what the exact commands are for clearing both the counters, I viewed a few Cisco sights, but they didn't work.

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Andy Bartkiewicz

Can we see port configs?
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ASKER

Is this what you need:

c_rack_.38#show run in gi1/0/28
Building configuration...

Current configuration : 100 bytes
!
interface GigabitEthernet1/0/28
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

c_rack_.38#


w_whub_.39#show run in gi1/0/50
Building configuration...

Current configuration : 100 bytes
!
interface GigabitEthernet1/0/50
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

w_whub_.39#
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Gil/0/28  connected     trunk      a-full    a-1000    10/100/1000BaseTX SFP

Gil/0/50      connected      trunk      a-full   a-1000      lO/lOO/lOOOBaseTX SFP
The configs look good. Are the SFPs Cisco? Have you tried replacing them?
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I replaced one of the switches. I  have NOT replaced the SFP's, I would have thought the cable should be replaced, but I'll try replacing the SFP's as well, to rule that out.
Also, do you know about how long the fiber run is?
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its not fiber, it's copper.  It's maybe 250 max.
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GigabitEthernetl/0/50 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is OOle.49a2.e532 (bia OOle.49a2.e532) MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usee,
reliability 255/255, txload 2/255, rxload 8/255 Encapsulation ARPA, loopback not set Keepalive not set
Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX SFP input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:17, output 00:00:00, output hang never Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 11 Queueing strategy: fifo Output queue: 0/40 (size/max)
5 minute input rate 32391000 bits/sec, 2976 packets/sec 5 minute output rate 10850000 bits/sec, 2097 packets/sec
19725676436 packets input, 28038619215369 bytes, 0 no buffer Received 73392706 broadcasts (8072815 multicasts)
0 runts, 31 giants, 0 throttles


GigabitEthernetl/0/28 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is b8be,bf33 -c51c (bia b8be.bf33.c51c) MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usee, reliability 255/255, txload 8/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive not set
Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX SFP input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output 00:00:10, output hang never Last clearing of "show interface" counters 03:32:25
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max)
5 minute input rate 4021000 bits/sec, 1525 packets/sec 5 minute output rate 32478000 bits/sec, 2801 packets/sec 26053842 packets input, 19541615850 bytes, 0 no buffer Received 311660 broadcasts (110338 multicasts)
0 runts, 0 giants, 0 throttles
207 input errors, 207 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 110338 multicast, 0 pause input 0 input packets with dribble condition detected 36065152 packets output, 48765968387 bytes, 0 underruns 0 output errors, 0 collisions, 1 interface resets 0 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out
79769 input errors, 50210 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 8072815 multicast, 0 pause input 0 input packets with dribble condition detected 11545923751 packets output, 3526017177844 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 PAUSE output 0 output buffer failures, 0 output buffers swapped out
SOLUTION
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Andy Bartkiewicz

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I have a tester, and it's all good, but I guess maybe It won't hurt to recrimp the ends of the cable
Avatar of David McMorris
Hi,

I had a similar issue where the port would jump between 1gbs and 100mbps speed. Turned out it was the cable.

Replace the cable with a new Cat.5e or Cat.6

Thanks,

David
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its a run between two buildings, and it's very difficult to run a new cable.
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I re crimped one end of the cable, as I had punched it down in the same spot, and it stopped working, so I'm hoping and suspeciting that's where the problem is at. I'll know in the next few weeks if it occurs again.  I cleared all stats on Thursday, and now looking at them again, it looks like there are 165 errors, and 99 CRC errors, is that normal to have that many errors in 3 days?
 
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No it isn't. I would get it replaced as soon as. You have a good business case.
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So then Since I re-crimped the cable on this end, and I'm getting those errors, I'll re-crimp it on the other end as well.   Could the problem be with the port itself on the switch?  Maybe I should just change the port on the switch?
You've said that you already tried changing the port?
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Well, I did temporarily to see if the link would come up, but I never left it on a new port for a few days to monitor the errors, to see if there are any errors.
Ah ok, yes try a new port and fingers crossed!
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so it's been 3 hours, and I just checked and there's 4 input errors and 1 CRC error. That seems to be that the issue is still there, I'll give it until Thursday to see how quickly those numbers increase.
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So it's been less than 24 hours, and there's 45 input errors, 11 CRC errors.  I looked at other ports, and at most there were a few CRC errors over months of time, so I think there's a problem somewhere.  I have already replaced 1 of the switches, I have re-punched one end of the cable to another port, and have also switched ports on the other switch, same issues.  I guess I should try to re-punch down the cable on the other end, and if that still doesn't solve my issue, then I can't see any other explanation that there's an issue with the cable, right?
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so it's been over 2 days now, and there are 48 input errors and 11 CRC, so it's been holding steady I guess.
I'll continue to monitor this next week.
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so it's been about a week now, or 4 days ago since my last post, and the states are 54 input errors, and 12 CRC errors, but with the weekend, since the organization was closed, I expect the numbers to be lower.  I'll check on Thursday and see what happens.
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Well, it's Thursday again, it's been over a week now, and the numbers are at 58 input errors and 12 CRC.  So it's good that it hasn't gone up a lot, but is that normal, are those figures normal in a production environment?  Is this something I need to be concerned about or to take any action?  The numbers from port 50, the old port were much higher, but then again, it was months worth of time to get to those numbers.
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thanks guys for your input, greatly appreciated.