gbic loop on catalyst 2960

Unanswered Question
Aug 13th, 2009

Hello,

I would like to know if there is a way to validate that a SFP type 1000baseLX is working properly on catalyst 2960.

I am looking for the loop feature that is available on routers.... but not on switches.

The topology is 2 catalyst 2960 switches with both SFP type 1000baseLX connected together with a fiber. This was working find but actually, the two interfaces are down/down.

The idea is to be sure that the problem is on the fiber and not on one of the SFP....

Thank You for your help.

I have this problem too.
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Marvin Rhoads Thu, 08/13/2009 - 07:25

UniDirectional Link Detection (UDLD) addresses your concern regarding the fiber. See http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_46_se/configuration/guide/swudld.html for more information.

For the SFPs themselves, you might want to review http://www.cisco.com/en/US/products/hw/modules/ps4999/products_tech_note09186a00807a30d6.shtml for more information.

Hope this helps.

viyuan700 Thu, 08/13/2009 - 08:02

You can also use hard loop means take a patchcord and connect transmitter to receiver (in LX you can connect directly but if you have a attenuator would be nice)similarly you can check your card at other end.

IF both cards are working, Now only fiber is left , you can loop the 2 fiber at other end and check whether your fiber have problems.

tquero Thu, 08/13/2009 - 08:36

Hi,

Thank You for your updates.

That means that there is no way to perform this loop in software mode with the IOS :-(

I thought about the possibility to physically loop with a patchcord but I am afraid to break the Rx LED of the SFP.

I will have a look on the LX specification to check the minimal distance.

The UDLD will not help me in this situation because both interfaces of both sides are in down/down status.

Anyway, thank you for your updates.

Regards,

Thomas Quero

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