Communication issue and conclusion from "Input errors, CRC"

Answered Question
Aug 19th, 2009

Folks, I have two switches:

4507 (port f3/2)---- 3750 (port f0/23)

All of sudden I see intefaces on 4507 f3/2 up/down. I go to 4507 and I see that the switchport f3/2 has some input errors and CRC errors. Then I see on 3750 switchport fa0/23 got way more errors. Also, output from show tech on 4507 switch showed message " Aug 19 10:37:22.549: %DTP-5-NONTRUNKPORTON: STANDBY:Port Fa3/2 has become non-trunk

Aug 19 10:41:57.180: %DTP-5-TRUNKPORTON: Port Fa3/2 has become dot1q trunk...". I imagine that such status that the port was a non-trunk was due to a bad communication (bad cable or bad switchport), correct?

Also, do you agree that based on the fact that I have way more input errors and CRC errors on switchport fa0/23 on the 3750 I can conclude that if it is a faulty switchport that would be likely be on the 3750? I will try to replace the cables and see if the problem goes away. Let me know if you have other approach in mind based on the data provided.

3750#show int

(...)

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

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

18682 packets input, 9509495 bytes, 0 no buffer

Received 18582 broadcasts (17576 multicast)

0 runts, 0 giants, 0 throttles

115699 input errors, 102042 CRC, 13657 frame, 0 overrun, 0 ignored

0 watchdog, 17576 multicast, 0 pause input

0 input packets with dribble condition detected

3750#show int f0/23 switchport

Name: Fa0/23

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: down

Administrative Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Voice VLAN: none

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk private VLANs: none

Operational private-vlan: none

Trunking VLANs Enabled: 2

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Appliance trust: none

4507#show int f3/2

FastEthernet3/2 is up, line protocol is down (notconnect)

(...)

Received 346732480 broadcasts (345361439 multicasts)

32 runts, 0 giants, 0 throttles

71 input errors, 39 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

20225802 packets output, 1643442465 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

4507#show int f3/2 switchport

Name: Fa3/2

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: down

Administrative Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: none

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk associations: none

Administrative private-vlan trunk mappings: none

Operational private-vlan: none

Trunking VLANs Enabled: 2

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

I have this problem too.
0 votes
Correct Answer by Lucien Avramov about 7 years 3 months ago

Your approach sounds overall correct.

Here is a useful doc for the CRC errors:

http://www.ciscotaccc.com/kaidara-advisor/lanswitching/showcase?case=K19375172

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
glen.grant Wed, 08/19/2009 - 16:12

Verify port settings on each match , if one end is set as auto for speed and duplex then the other end "must" be set as auto also. Sounds like a speed/duplex mismtach.

news2010a Wed, 08/19/2009 - 16:36

It turned out it was a cable miswired. Once I asked to rebuild and repatch cable, things worked.

Lucien Avramov Wed, 08/19/2009 - 18:58

Great.

That is usually most of the times the issue. If no one touches the duplex settings, it wont happen.

Glad you resolved it.

Actions

This Discussion