Can you connect a 10Gb SFP+ to a standard 1Gb SFP?

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Nov 16th, 2011
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I'm looking at provisioning a Catalyst 4500 with a WS-X4712-SFP+E module to allow for future 10Gb connectivity via 10Gb SFP+ interfaces.  These cards are backwards compatible with standard 1Gb SFP interfaces but I'm wondering about the other way around; ie. can you populate these blades with 10Gb SFP+ interfaces when they connect to Catalysts with only 1Gb SFP interfaces at the other end? 

The data sheets don't really expalin this.  I appreciate that it seems pointless getting 10Gb SFP+ interfaces for the 4500 when it's only 1Gb at the access layer end, but these access switches will be replaced in the near future (~12 months) and if the 10Gb SFP+ interfaces support connections at 1Gb speeds upfront, it would mean I could retain these interfaces when the access switches upgrade to 10Gb connectivity capabilities down the track.

Can anyone clarify if the 10Gb SFP+ interfaces are compatible with 1Gb SFP's or only other 10Gb SFP+ interfaces?

Thanks in advance for your help.


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flokki123 Thu, 11/17/2011 - 00:01
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hi dean,

first i want to say that i never tried it myself so this statement is just what i think.

10Gbit LR uses single mode fiber and a 1310nm laser. i think if you stick with that characteristics on the SFP side then you could have a chance to make that work. e.g. 1000Gbit-LX also works with a single mode fiber and also uses a laser in the range of 1,270–1,355 nm. though if these settings are same on both sides it might work.

but maybe someone in this forum has more info and can clarify this.



smith.dean Thu, 11/17/2011 - 00:22
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Thanks for the feedback Florian. Appreciate your input. I don't have one to test out but would probably be reluctant to even if I did. I'd be cautious of frying the SFPs as I assume the SFP+ power outputs would be more than the 1Gb modules. Would be good to get some definitive answers on it though. I'm really surprised the product page is so vague on it.


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flokki123 Thu, 11/17/2011 - 01:17
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had a little look around the net and found that 1Gb and 10Gb fiber are not auto-negotiable. so that would mean that the 10Gb interface is fixed to 10Gb and will not slow down and thus the communication wouldnt work.

guess your scenario wont work.

smith.dean Thu, 11/17/2011 - 01:56
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thanks for the effort Florian. I was 95% sure that would be the case. Was just after that 5% confirmation!


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