Are there any SFP+ adapters to connect 2.5 GBe RJ45?

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sofakng

Member
Apr 27, 2011
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I'm using a UDM Pro with a UniFi US-48 switch and both have 10G SFP+ ports.

However, one of my new PCs has a 2.5 GBe RJ45 port.

Are there any SFP+ adapters to convert from 2.5 GBe RJ45 to SFP+ ? If so, are any recommended for compatibility with the UniFi US-48 (or UDM Pro) ?
 

LodeRunner

Active Member
Apr 27, 2019
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You could try the Mikrotik S+RJ10 SFP. I forget what the other one is that would work. An Aquantia of some sort. They convert a SFP+ to copper and support 1/2.5/5/10G speeds. How the UniFi switch will react to that is another matter that I cannot speak to.
 

newabc

Active Member
Jan 20, 2019
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Ubiquiti and FS brands have 10/5/2.5 multiple Gig rj45-to-sfp+ module.

Brand ONTi has a 2.5g rj45 SFP module(link). (That means 2.5Gbps only.)
I bought 1, but haven't got chance to test it yet.

ONTi will ask about what brand is your switch before shipping out.
 

LodeRunner

Active Member
Apr 27, 2019
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I think this is the correct answer right here
There are several reports in this forum of Aquantia based SFPs working at multigig speeds in non-nBaseT aware switches. Somewhat less success with the non-Aquantia SFPs. Specifically AQS-107 based SFPs have been working properly at 2.5 and 5 G in ICX switches and others.
 
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mattventura

Active Member
Nov 9, 2022
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I always thought the switch itself must support such speeds, otherwise it wouldn't work?
NBase-T (or even just plain 1/10G) modules are....weird. Since 2.5G SFP+ support is uncommon (and 5G even less so), these modules typically will want to talk to the switch side at 10G, and handle the RJ45 speed negotiation themselves (they're essentially a tiny ethernet bridge). I have one plugged into a CRS305, and the switch always shows a 10G connection even if the actual link is 1G. Even if you do have support for 2.5G SFP as the CRS305 does, it won't work at all if you try to force 2.5G from the switch side, because the SFP side of the transceiver doesn't do 2.5G.
 

StarsAndBars

New Member
Jul 13, 2020
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Ubiquiti and FS brands have 10/5/2.5 multiple Gig rj45-to-sfp+ module.

Brand ONTi has a 2.5g rj45 SFP module(link). (That means 2.5Gbps only.)
I bought 1, but haven't got chance to test it yet.

ONTi will ask about what brand is your switch before shipping out.
Ever get a chance to test this? I am tempted to order one with as cheap as it is.
 

Mithril

Active Member
Sep 13, 2019
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Any new updates? I have some brocade ICX switches I wouldn't mind adding a 2.5/5G port to (I'm fine with a 10G RJ45 that can negotiate down to 2.5/5G so long as it works :) )
 

blunden

Active Member
Nov 29, 2019
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Any new updates? I have some brocade ICX switches I wouldn't mind adding a 2.5/5G port to (I'm fine with a 10G RJ45 that can negotiate down to 2.5/5G so long as it works :) )
Based on responses in other threads, the AQS-107 based SFPs work well in cases like these. Other ones often have issues apparently.

My understanding is that the AQS-107 based SFPs tend to be more expensive and are getting harder to find though. I'm not sure if Marvell/Aquantia even makes them anymore.
 

blunden

Active Member
Nov 29, 2019
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No need to chase the AQS-107 made out of Unobtainium. Try "ASF-10G2-T" from 10GTek. Aquantia still, and with all the magic tricks, but newer.
Awesome! :) I was afraid modules that handled this correctly were going to disappear entirely.
 

casperghst42

Member
Sep 14, 2015
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The question is whether they do it well though? :) There are modules that technically support it but that have all sorts of issues in practice.
So very true, I was having problems with them in my Ruckus ICX 7150 P12C, they were running too hot with my TS4 (2.5GbE), then I got a FS module instead - that promptly killed it self by over heating (got it replaced under warranty).

I think for the price they work quite well, if you have a switch which have active cooling.