What should I do about broken SFP ports?

rweir0001 · ‎04-29-2015

Hi,

I have a port channel configured between a Cisco WS-C3850-48T and a Cisco Catalyst 2960-X Series switch. A couple of days ago two of the ports went down on the C3850 and I traced the problem to the SFP ports on the 2960. I tried plugging the cable into all four of those SPF ports (with the other end connected to the C3850) but the port light doesn't come on at all. I have eliminated the possibility of a bad cable or SFP transceiver because I can plug it into the SFP ports of other switches without an issue. Essentially, it looks like a hardware issue on the switch and I'm not sure how to handle it because unplugging everything from the switch and returning it isn't really a viable option.

Has anyone else had issues with SFP ports? And if so, how did you handle it?

Joseph W. Doherty · ‎04-29-2015

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My experience either you replace the faulty equipment or you live with the broken port(s).

Of course, if you have a soldering iron, a logic analyzer, and don't mind voiding any still valid warranties, I guess you can try to repair it yourself. ;)

rweir0001 · ‎04-29-2015

Haha. Thanks. Those do seem like the only two options but I was hoping for some magical cure because I don't like either one of them.

johnlloyd_13 · ‎04-30-2015

hi,

there's a professional kit to clean SFP and fibre optics but if you want a cheap fix, try to clean the SFP contacts (can also try to fibre optic cable tips) with a cotton swab/q-tip and damp of rubbing/isopropopyl alcohol.

rweir0001 · ‎05-01-2015

Thanks. If the issue happens again I'll look in to doing that.

Liam Kenneally · ‎05-01-2015

Hi rweir0001,

Before you assume the SFP ports are faulty, have you looked under the interface of the SFP ports.

It could be a spanning-tree or port security issue. This could be causing the ports to enter an err-disabled mode. This would explain why the ports work again after a switch reboot.

If you run into the same problem try running the following command(Note I am currently at home so have run the command from packet-tracer. But you will see a similar output)

Switch#sh interfaces gigabitEthernet 0/1

As you can see from the below it says "line protocol is down" then "(disabled)"

If you have a port violation this may say "(Err-disabled)" or on the newer 2960Xs some other helpful information.

GigabitEthernet0/1 is down, line protocol is down (disabled)

Hardware is Lance, address is 0001.63dd.ce19 (bia 0001.63dd.ce19)

MTU 1500 bytes, BW 1000000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Half-duplex, 1000Mb/s

input flow-control is off, output flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:08, 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: 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

956 packets input, 193351 bytes, 0 no buffer

Received 956 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

2357 packets output, 263570 bytes, 0 underruns

0 output errors, 0 collisions, 10 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

If you are getting port violations, I would look at the show logging command and see what is causing the port to hit a violation.

Just my two cents woth!

HTH,

Kind Regards,

Liam

rweir0001 · ‎05-01-2015

That's great advice, Liam, thanks! I'll take that into consideration if the problem resurfaces.

Liam Kenneally · ‎05-01-2015

No problem at all! :) Also you mentioned you had the SFPs in a Port-Channel. So I would also look under the Po interface :)

Fingers crossed the problem doesn't re-surface.

Kind Regards,

Liam

rweir0001 · ‎05-01-2015

Cool. Thanks.

rweir0001 · ‎04-30-2015

I resolved the issue by reloading the affected 2960 switch and the SPF ports started functioning again.