2960X down-when-loop

[guillaume.chartrand]

Hi, I have a Cisco Catalyst 2960X-48LPS-L iOS version 12.2(55r)SE

I have a port linked to another switch (D-Link DGS-3120)

The config of the port is only

switchport access vlan XXX

I suspected some loop on the link so I try to activate the "down-when-loop" command on that port

When I do that, automaticly the port going down, but not in errdisable. It's state is down (not connected).

After that I remove the commande down-when-loop with "no down-when-loop" on that port. Shutdown the port and renable it. Whatever I plug into the port, the port still stay down (not connected). The only solution to make it right again is reload the switch so it's not a real solution.

How can I resolve that without reload? I try unplug, plug again, plug a switch or a laptop, Nothing happens to port stay down (not connected)

[Georg Pauwen]

Hello,

try to enable and the disable keepalives on the affected port:

2960(config-if)# keepalive 10
2960(config-if)# no keepalive

[guillaume.chartrand]

Nothing change. I try to plug again a switch on that port and the port stay down

[Georg Pauwen]

Hello,

can you post the output of 'show interface x' when the port is down ?

[guillaume.chartrand]

GigabitEthernet1/0/14 is down, line protocol is down (notconnect)
  Hardware is Gigabit Ethernet, address is 203a.0747.368e (bia 203a.0747.368e)
  Description: Laboratoir
  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Auto-duplex, Auto-speed, 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 never, 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 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected

     0 packets output, 0 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