Cisco 3750G intermittent amber/green blinking

[idscomm]

Folks,

I ran into a problem this afternoon and I can't find the cause or solution.

I have a Cisco 3750G in a LAN, I have a PoE device connected to port #16, configure as access port. The device is a Unifi Cloud Key which is powered and the lights are blinking green on the switch which shows that the port is working.  Then I noticed that randomly the light on the switch for port #16 starts going from green to amber for 5-10 seconds, then goes back to green and so on.  I have no connectivity whatsoever on this port no matter what color is the light.

Now, I tried to connect a laptop on port #16 and it worked properly (minus a few crc/input errors). Then I connected my Unifi Could Key into port #15 and it worked properly as well.  Both ports are access port with the same parameters (unless I missed something).

For now I left my cloud key in port #15 as it is working properly.  Any idea what the problem might be?

Thanks!

Dom

[idscomm]

Output of those commands as requested... Guess it is not good when my device is connected :-/

sh cable tdr int Gi1/0/16 output (with other end of cable unplugged)
--------------------------------------------------------------------

TDR test last run on: April 30 18:01:38

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/16 auto Pair A 0 +/- 4 meters N/A Open
Pair B 0 +/- 4 meters N/A Open
Pair C 1 +/- 4 meters N/A Open
Pair D 1 +/- 4 meters N/A Open


sh cable tdr int Gi1/0/16 output (with other end of cable plugged)
------------------------------------------------------------------

TDR test last run on: April 30 18:05:11

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/16 auto Pair A 0 +/- 4 meters Pair A Fail
Pair B 137 +/- 4 meters Pair B Fail
Pair C 151 +/- 4 meters Pair C Normal
Pair D 152 +/- 4 meters Pair D Normal




sh version output:
------------------

Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 12.2(55)SE12, REL
EASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2017 by Cisco Systems, Inc.
Compiled Thu 28-Sep-17 02:29 by prod_rel_team
Image text-base: 0x01000000, data-base: 0x02D00000

ROM: Bootstrap program is C3750 boot loader
BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.2(44)SE5, RELEASE SOFTWARE
(fc1)

cisco3750g uptime is 23 hours, 39 minutes
System returned to ROM by power-on
System restarted at 18:16:47 ADT Sun Apr 29 2018
System image file is "flash:/c3750-ipbasek9-mz.122-55.SE12/c3750-ipbasek9-mz.122
-55.SE12.bin"


This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

cisco WS-C3750G-24PS (PowerPC405) processor (revision H0) with 131072K bytes of
memory.
Processor board ID FOC1338W42B
Last reset from power-on
3 Virtual Ethernet interfaces
28 Gigabit Ethernet interfaces
The password-recovery mechanism is enabled.

512K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address : EC:30:91:15:EB:00
Motherboard assembly number : 73-10217-12
Power supply part number : 341-0108-04
Motherboard serial number : FOC133842GL
Model revision number : H0
Motherboard revision number : C0
Model number : WS-C3750G-24PS-S
System serial number : FOC1338W42B
Top Assembly Part Number : 800-26855-05
Top Assembly Revision Number : E0
Version ID : V10
CLEI Code Number : COMB400BRC
Hardware Board Revision Number : 0x09


Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
* 1 28 WS-C3750G-24PS 12.2(55)SE12 C3750-IPBASEK9-M


Configuration register is 0xF

[idscomm]

and that is with a new 7' Cat6 cable... still no connectivity

TDR test last run on: April 30 18:10:56

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/16 auto Pair A 2 +/- 4 meters Pair A Normal
Pair B 1 +/- 4 meters Pair B Normal
Pair C 2 +/- 4 meters Pair C Normal
Pair D 1 +/- 4 meters Pair D Normal

[Leo Laohoo]

Post the complete output to the command "sh interface Gi1/0/16 controll" again (with the new cable).

[idscomm]

GigabitEthernet1/0/16 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is ec30.9115.eb10 (bia ec30.9115.eb10)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 240/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:01, output hang never
Last clearing of "show interface" counters never
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 0 bits/sec, 0 packets/sec
5 minute output rate 7000 bits/sec, 2 packets/sec
1519 packets input, 1220478 bytes, 0 no buffer
Received 164 broadcasts (64 multicasts)
0 runts, 0 giants, 0 throttles
4467 input errors, 431 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 64 multicast, 0 pause input
0 input packets with dribble condition detected
7242 packets output, 1807501 bytes, 0 underruns
7242 packets output, 1807501 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 PAUSE output
0 output buffer failures, 0 output buffers swapped out

Transmit GigabitEthernet1/0/16 Receive
658455 Bytes 942485 Bytes
895 Unicast frames 640 Unicast frames
1040 Multicast frames 29 Multicast frames
247 Broadcast frames 53 Broadcast frames
0 Too old frames 71730 Unicast bytes
0 Deferred frames 5584 Multicast bytes
0 MTU exceeded frames 3392 Broadcast bytes
0 1 collision frames 0 Alignment errors
0 2 collision frames 130 FCS errors
0 3 collision frames 0 Oversize frames
0 4 collision frames 0 Undersize frames
0 5 collision frames 50 Collision fragments
0 6 collision frames
0 7 collision frames 115 Minimum size frames
0 8 collision frames 1193 65 to 127 byte frames
0 9 collision frames 781 128 to 255 byte frames
0 10 collision frames 946 256 to 511 byte frames
0 11 collision frames 343 512 to 1023 byte frames
0 12 collision frames 69 1024 to 1518 byte frames
0 13 collision frames 0 Overrun frames
0 14 collision frames 0 Pause frames
0 15 collision frames
0 Excessive collisions 3232 Symbol error frames
0 Late collisions 8 Invalid frames, too large
0 VLAN discard frames 0 Valid frames, too large
0 Excess defer frames 679 Invalid frames, too small
713 64 byte frames 0 Valid frames, too small
477 127 byte frames
183 255 byte frames 0 Too old frames
449 511 byte frames 0 Valid oversize frames
181 1023 byte frames 0 System FCS error frames
179 1518 byte frames 0 RxPortFifoFull drop frame
0 Too large frames
0 Good (1 coll) frames
0 Good (>1 coll) frames

[Leo Laohoo]

The output is still showing the cable is still faulty.
What is the distance between the port and the downstream client? Does this go to a patch panel?

[idscomm]

7' between the switch port and the device, connected directly to the switch.

[Leo Laohoo]

Try a different port on the switch and keep an eye out for the "input errors".

[idscomm]

I'll put it back on port #15 where it seemed to work properly...

[rasmus.elmholt]

Have you looked on the female connector in the switch on port 16, maybe some of the pins are bend or corroded?

[idscomm]

I’ll have a look for sure, maybe make sure it’s clean too. Thing is that it should have affected the other device I connected to do my test :-/. For now the port is empty, to be on the safe side but I only have 2 empty ports on that switch ...

[Leo Laohoo]

Can you post the complete output to the command "sh post"?

[rasmus.elmholt]

If the interface turns amber it is most likely a STP problem.
Do you see anything about STP in the log?

#debug spanning-tree event will tell you if the port changes state.

And remember portfast on the port as well.

[idscomm]

Hi there,

I ran a quick sh conf for the port #16, this is the output:

interface GigabitEthernet1/0/16
switchport access vlan 10
switchport trunk native vlan 10
switchport mode access
switchport nonegotiate
no cdp enable
spanning-tree portfast disable
spanning-tree bpduguard enable

Pretty simple config for now, trying to pinpoint the issue.  Should spanning-tree portfast should en enable?

Thanks!!

[rasmus.elmholt]

Hi
I would enable portfast on the port for an end device like this "server".
To make sure your STP doesn't re-converge when the port goes up or down.

And remove the switchport trunk statement.

This should be an accessport.

#no switchport trunk native vlan 10

[idscomm]

ok, I will make the correction and keep you posted. Thanks!