SFP port troubleshooting

[BeckyBoo123]

Hi All,

I am hoping that someone may be able to shed some light on a strange issue we have.

We have two new Catalyst 2960-48PST-S switches both of which have an 1000BaseSX SFP module installed in GigabitEthernet0/1.

Each transceiver is securely installed as each switch hows:

SwitchA#show int gigabitEthernet0/1 transceiver properties
Diagnostic Monitoring is not implemented.
Name : Gi0/1
Administrative Speed: 1000
Administrative Duplex: full
Administrative Auto-MDIX: on
Administrative Power Inline: N/A
Operational Speed: 1000
Operational Duplex: full
Operational Auto-MDIX: off
Media Type: 1000BaseSX SFP

Each port on both ends is also trunked:

interface GigabitEthernet0/1
 description Fibre link to Switch B
 switchport mode trunk

In the lab during setup, I was able to to connect the two switches together using the SFP port and ping each other.

Now the switches have been placed into a live environment and connected together usings a longer fibre cable, I cannot replicate the tests. I cannot see the second switch (SwitchB) from the core switch (SwitchA).

The fibre cable has been tested and light can be seen at each end, so we know the cabling is good.

Can anyone suggest any tests for diagnosing this issue.

[Seb Rupik]

Hi there,

Always worth a shot, have you tried changing the polarity of the fibre?

cheers,

Seb.

[BeckyBoo123]

Hi there, do you mean just switch the cables around?

In between each switch there is a fibre patch panel which I guess has formed part of the testing to prove the fibre cable was letting light through.

Do you think it would be worth while to simply unplug the cable from the SFP port to the panel and turn the cable around?

[Seb Rupik · Accepted solution]

'Break' the cable and swap the position of the strands when inserted into the SFP:

http://www.shanekillen.com/2013/07/changing-polarity-txrx-of-fiber-patch.html

cheers,

Seb.

[BeckyBoo123]

Hi,

Fantastic thank you. This worked perfectly!