No connectivity between switches...

Answered Question
May 30th, 2007

Hi Guys,

I have two Cisco Catalyst 2960G switches that I am trying to trunk together.

Each switch has a SFP transciever module plugged into the gi0/24 GBIC port. My setup is like this:

switch1----media converter******media converter-----switch2

- is LC to ST fiber

* is cat5e STP straight through cable

The only reason we are using the media converters is because we don't have any LC to LC fiber. Media converters both state that links are active (flashing lights), but when I do a "show cdp neighbors" on either switch, nothing shows up. The interfaces on both switches show as (notconnect). Trunk ports ARE properly configured to trunk..

Anybody have any ideas? Help would be greatly appreciated.

-Chris

I have this problem too.
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Correct Answer by jasonrandolph about 9 years 6 months ago

That would very likely be your issue then. SFPs are typically gigabit only. Fiber transceivers from cisco are pretty much either 100base FX or 1000base FX.

To prove your configuration you'd be better off duplicating the trunk config on a copper port and using a crossover cable to verify.

This is why you couldn't hard-set the port speed. It's already hard-set at gigabit. What is the model of SFP being used?

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chris.lepa Wed, 05/30/2007 - 12:22

You mean LC to LC? We don't have any currently, and this isn't in production, so it isn't too important. I'm just power conditioning these switches and making sure they connect properly before we send them out to the remote site. And yes, they are in the same VTP domain.

jasonrandolph Wed, 05/30/2007 - 12:30

Duh, if I'd read a little more closely.

Are these standard gigabit SFPs, and are the media converters gigabit fiber.

chris.lepa Wed, 05/30/2007 - 12:31

Actually the media converters only operate at 100base-FX to 100base-TX. I tried to hardcode a speed of 100 in on the trunking interface, but it wouldn't accept the command.

Correct Answer
jasonrandolph Wed, 05/30/2007 - 12:36

That would very likely be your issue then. SFPs are typically gigabit only. Fiber transceivers from cisco are pretty much either 100base FX or 1000base FX.

To prove your configuration you'd be better off duplicating the trunk config on a copper port and using a crossover cable to verify.

This is why you couldn't hard-set the port speed. It's already hard-set at gigabit. What is the model of SFP being used?

chris.lepa Wed, 05/30/2007 - 12:30

Yes, the LC side of the cord is plugged into the SFP transciever on the switch and the ST side is plugged into the media converter (for both switches).

What type of transceivers? Sometime's there's a MDI-X, or maybe some vendor specific equivelent switch settings that have to be made. For transition M/Cs the MID-X settings must be different on both ends of the MC---copper---MC side.

A test would be to move the whole fiber>copper>fiber link to a known good switch fiber interface and eliminate the patching process as a problem.

chris.lepa Wed, 05/30/2007 - 12:54

After consulting one of my co-workers, he seems pretty confident as well that the problem lies with the converter only supporting 100Mbs. Thanks for the help guys.

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