2960s switch drops connection

[Caughtflying]

We have a 2960s switch which is a server farm switch connected directly to the core switch via fiber cable.

The problem is that it drops the connection to the servers. don't know why that happens but when i disconnect the fiber cable and reconnect it, It works fine for a period of time and it disconnects again.

We changed the switch with another 2960s switch and restored the configuration to it .. I disabled the spanning tree on the servers vlan and it get disconnects every period of time it may take hours to disconnect or drop the connection.

so any ideas why is that happening? 

[Mark Malone]

Hi

can you post the show interface of the uplink and the show run int x/x

have you tried changing the gbic , is the switch under pressure when it happens

Shouldn't be STP if it only 1 uplink

anything appearing in show logging when it happens

[Caughtflying]

Hello Mark,

Thx for the reply.

I've changed the Gbic before i write this post and i am waiting to see any difference and the switch drops the connection lately in a vacation it wasnt under any pressure.

below is the show commands you asked for

show run int#

SRV-SW#show run int gi1/0/50
Building configuration...

Current configuration : 39 bytes
!
interface GigabitEthernet1/0/50
end

Show int#

GigabitEthernet1/0/50 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 2834.a265.1132 (bia 2834.a265.1132)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, 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 592000 bits/sec, 279 packets/sec
  5 minute output rate 1181000 bits/sec, 255 packets/sec
     35107392 packets input, 7034500506 bytes, 0 no buffer
     Received 18900918 broadcasts (16148998 multicasts)
     0 runts, 0 giants, 0 throttles
     12 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 16148998 multicast, 0 pause input
     0 input packets with dribble condition detected
     37415611 packets output, 26011747158 bytes, 0 underruns
     0 output errors, 0 collisions, 2 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

[Mark Malone]

Hi the output looks ok not many errors, lot of traffic gone though it 208 gb

are you monitoring the link at all with software or have you logged in when the issue is occurring and check the tx/rx to see if its overloaded or if the cpu is spiking ?

Is the other side of the link generally clean as well?

[Caughtflying]

Hello,

no am not monitoring with a software. neither checked the tx/rx or cpu overload but i may check it if it happens a next time that if the gbic didn't solve the problem.

i checked the connection on the core switch also reconnected the fiber channel but it didn't make any difference .. it get to work again after i reconnect the server farm switch fiber cable.

BR,

[Mark Malone]

Yes there good things to check during the issue ,if interface is completely overloaded it may drop

does nothing show in the logs when the issue occurs on either side?

you could check the show controller g1/0/50 check the error statistics section at the end of the output

show interface transceiver can be good if supported on your device

your not breaching the sfp guidelines at all either below just in case

1000BASE-SX SFP for Multimode Fiber Only

The 1000BASE-SX SFP, compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50 μm multimode fiber links up to 550 m and on 62.5 μm Fiber Distributed Data Interface (FDDI)-grade multimode fibers up to 220 m. It can support up to 1km over laser-optimized 50 μm multimode fiber cable.

[Caughtflying]

I agree with you but my issue here it does not just drop the connection it keeps flapping. when i try to ping the servers from my workstation it shows a lot of request time out.

I found the other SFP clip broken. is this could be the problem? .. till now everything is working fine since i changed the SFP this morning. I\ve attached a couple of pics of the one i've changed.

We dont have this kindda distances its only a couple of meters about 6 or 7 meters.

[Mark Malone · Accepted solution]

If its flapping that's different issue and yes those clips not being secure is an issue as the fibre can become loose easily  , if even a slight loose connection will result in lost packets constantly , run extended pings with heavy payload of 1500 and if its still good after several thousand no drops that was most likely your issue

[Caughtflying]

Well i pinged more than 2000 packets lost nothing and everything is working fine. 

will see tomorrow hows things going as am getting off work now.

thx for the tips .. will follow up tomorrow

[Caughtflying]

Well everything is stable now .. i think the problem was in the SFP transceiver.

Thx for helping out especially the technical tips

BR,