01-11-2018 06:27 AM - edited 03-08-2019 01:23 PM
So I have switch A in our library that i replaced here recently. After replacing it and getting the link back to Switch B in an outbuilding with the same port configuration, I have found that Switch B's port that the link will start flashing Green like normal, then do slow flashes to amber, then Solid Green, then normal again and restart the process about 2 minutes later.
Ever since this has been happening, the outbuilding end points have been having intermittent connection issues. They are up for about 10 minutes, will drop for a few minutes then come back up.
Any ideas?
Switchport A's Link Info:
GigabitEthernet1/0/47 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 706b.b9f2.0baf (bia 706b.b9f2.0baf)
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/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 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: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 7000 bits/sec, 7 packets/sec
5 minute output rate 254000 bits/sec, 131 packets/sec
2873824 packets input, 670577609 bytes, 0 no buffer
Received 106846 broadcasts (45328 multicasts)
51 runts, 0 giants, 0 throttles
123 input errors, 68 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 45328 multicast, 0 pause input
0 input packets with dribble condition detected
24193734 packets output, 7131128083 bytes, 0 underruns
0 output errors, 0 collisions, 2 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
Switchport B's Link Info:
GigabitEthernet1/0/24 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 00eb.d570.a218 (bia 00eb.d570.a218)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/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 00:00:00, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5502
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 505000 bits/sec, 204 packets/sec
5 minute output rate 12000 bits/sec, 14 packets/sec
1618719015 packets input, 431710085926 bytes, 0 no buffer
Received 1013462742 broadcasts (262779649 multicasts)
0 runts, 0 giants, 0 throttles
44 input errors, 16 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 262779649 multicast, 0 pause input
0 input packets with dribble condition detected
278056290 packets output, 51912585069 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
Any thoughts would be appreciated.
01-11-2018 06:52 AM
Hi there,
Both ends of the link are showing CRC errors. A sure sign that you should check and replace the connecting cables.
cheers,
Seb.
01-11-2018 07:01 AM
01-11-2018 07:13 AM
01-11-2018 07:32 PM - edited 01-11-2018 07:32 PM
I agree, looks like a LAN loop. Are you running spanning-tree portfast on user facing ports without spanning-tree bpduguard, or has someone inadvertently put portfast on a switch-to-switch trunk on that campus?
01-12-2018 05:37 AM
That's exactly what is was. Switch A had portfast enabled because I had to use an alternate switchport for the link, and never turned it off. Thanks a million!
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