Cisco 4431 router

[Stephen Sisson]

Hello everyone,

We have a Cisco 4431 router and need your help with the SFP modules - for some reason all four remain down know matter how we configure them, if we plug a copper CAT5 e cable into the port marked GI0/0/0 that interface comes online.
We are using SFP that are supported with single mode fiber
Need your help to get the interfaces online.

Thank you

[Reza Sharifi]

Hi,

Have you tried replacing the SFP and/or the patch cord?

Is the SFP single mode?

Is the fiber single mode?

Have you tried crossing the stands at one end of the patch cord?

HTH

[Stephen Sisson]

Hi

Using single mode SFP with single mode patch - remove this from the Cisco 4431 router and plug into a Cisco 3750 switch everything comes up up, so that tells me everything is working including the fiber pairs crossed correctly

[Reza Sharifi · Accepted solution]

You have taken the correct steps to troubleshoot both the fiber and the SFP.

So, the port can be copper or fiber right?

If this is the case, can you try adding "media type fiber" under the interface and test again?

HTH

[Stephen Sisson]

Dude, you are the man

Changing the media type to SFP brings the interface online, (makes sense)

Thank you so much

[Reza Sharifi]

Glad to help Stephen.