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Beginner

Connecting two switches through a fiber cable

Hey guys...

I have a basic knowledge of network and need some help.

I need to connect a single 3750G - 48 ports switch to a single 2960 - 48 ports switch and it needs to be through a fiber. So, PCs connected to one switch would reach the PCs from the other switch.

I see that the 3750G switch has (What I believe is) 4 SFP ports and the 2960 has 2 SFP ports.

Well, I have erased (write erase) the configuration of both switches, so they have the default cisco config.

I have plugged in the SFP transceivers at both switches and used a LC fiber to connect them.

I saw that the Vlan1 was down (sh ip inter brief). So, I did a no shut at interface VLAN 1 on both swtiches...

However, the lights are still off on both SFP ports.

Do I need to configure anything on the switches to make them see each other?

Because if I use a simple UTP 5e cable to connect them I don´t need to do anything. They just start seeing each other... Do I need to do something special when using these SFP connections?

I also don´t know the SFP part numbers I´m using on them...A guy who works with Cisco gave them to me and said it "should" work.

So, I don´t know if it´s a configuration problem, a SFP model problem or both??

Any help is appreciated!

Thanks

2 ACCEPTED SOLUTIONS

Accepted Solutions
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Hall of Fame Expert

Hi,

If there is no link light when you connect the fiber port, you have most likely a physical layer issue.

So, check to see if your SFPs are multimode or single mode

once you find what type of SFP you are using, make sure you also use the right fiber patch cord.

so single mode SPF with Single mode fiber patch cord and multimode SFP with Multimode fiber patch cord.

If cables and SFPs are not the issue, then some 3rd party SFPs do not work with Cisco devices.

HTH

Reza

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Rising star

Hi,

can you ensure the sfp type at both end. You can issue sh interface command and see for below output

"media type is SX"  the media type need to be same at both end.possible types are SX,LX,ZX.

Regards

Mahesh

View solution in original post

3 REPLIES 3
Highlighted
Hall of Fame Expert

Hi,

If there is no link light when you connect the fiber port, you have most likely a physical layer issue.

So, check to see if your SFPs are multimode or single mode

once you find what type of SFP you are using, make sure you also use the right fiber patch cord.

so single mode SPF with Single mode fiber patch cord and multimode SFP with Multimode fiber patch cord.

If cables and SFPs are not the issue, then some 3rd party SFPs do not work with Cisco devices.

HTH

Reza

View solution in original post

Highlighted
Rising star

Hi,

can you ensure the sfp type at both end. You can issue sh interface command and see for below output

"media type is SX"  the media type need to be same at both end.possible types are SX,LX,ZX.

Regards

Mahesh

View solution in original post

Highlighted
Beginner

Hello guys,

Thank you for the quick answers!

The problem was really the SFP transceiver... It was a Cisco transceiver, however, I think the model I was using wasn't the correct one...

Once I replaced it, everything started working.

I appreciate your help.

JME

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