2500Base-X support


I can’t find any information on 2500Base-X (HSGMII) support besides some kernel patches.
Is it supported by hardware? Are there any plans to support it with patches/mainlining?

LS1088A datasheet says “Up to two SGMII supporting 2500 Mbps”.

Thank you

It’s theoretically possible, but currently requires a change to the systems boot settings, just like 1G SFPs.

A limitation of the LS1088A is that you can’t have a 10G interface at the same time as 2.5G. 2x2.5G or 1x1G,1x2.5G is ok.

Do you have SFPs that do 2500Base-X?

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This one: https://www.fs.com/products/133619.html
It’s confirmed working at 2.5Gbps on a few devices. (BCM57810S, Ubiquity ES-16-XG…)

One interface locked at 2.5Gbps is perfectly fine as long as another one runs at 10Gbps.
Something like bl2_qspi_xg1_2.5g.pbl

Current 10G+1G uses this:

According to this:

I need to change SRDS_PRTCL_S1_LN1=3 to SRDS_PRTCL_S1_LN1=2

But this combination is not present in the table. Does that mean XFI and SGMII@2.5G are mutually exclusive?

Ah, I don’t have a GPON OLT (or a willing ISP) so can’t test that. But I’ve ordered their 2.5GBASE-T to try.

Yes, as I noted above, as far as I am aware you can’t do 10G (XFI) at the same time as 2.5G SGMII. I believe it has to do with the PLLs not being able to provide a clock for both 2.5G and 10G.

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That’s a shame, I’ll have to keep searching for a solution until NG-PON2 arrives…
As far as I know their 2.5GBase-T SFP uses XGMII so that might not work.

Thanks for the help

Hi all,

We have done some testing with 2.5G devices recently.

Unfortunately we have determined that current Ten64 production boards are unable to use 2.5G SFP’s.
The cause is the 10G retimer (DS110DF410) not supporting 2.5G rates.

However, an alternative part exists that can support 1G, 2.5G and 10G which we might build with in the future.

Futhermore, there appear to be interoperability issues between the “SGMII 2.5” in the LS1088 and the 2500BASE-X in many of these SFPs. I haven’t been able to get the FS 2500BASE-T working yet (on a board with the 10G retimer bypassed), it might be due to conflicting settings between them.

If anyone is interested in testing Ten64 boards with 2.5G SFP support, let us know.


I got two RJ45 tranceivers that can provide up to 10G support. Now, when I check the prices for 10G support for a notebook, these are just insane. Consequently, it would be nice to connect my notebook just with a 5G dongle. Is it possible to run the LS1088A with 5G? I would assume the tranceivers shouldn’t be the issue?

The LS1088A does not have a 5Gb Ethernet mode but that isn’t a practical issue if you want to connect to a 5GBase-T, or even 2.5GBase-T devices.

Many of the 10GBase-T SFPs (e.g Mikrotik S+RJ10) can rate adapt down to 1, 2.5 and 5GBase-T inside the module. The link between the module and the host is still 10G but the module can use flow control to ensure the host doesn’t send frames too fast.

If you have two 10GBase-T SFPs, be careful as they get very hot and don’t like to operate installed next to each other. I have been able to get around this by using an extender cable (like CVT-S/S-Cage-010) so one SFP is outside the chassis.

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I’ve got a 2.5Gbe SFP fiber ONT on the way. While I can configure it to run at 1G (I think), I’d like to use it to its full potential. My current plan is an intermediary device to act as a switch, but I’d love to see about getting it to work directly. Depending on how involved the hardware replacement is, I’m even down to try it myself. :slight_smile:

I haven’t been able to get my hands on the 2.5G capable part (DS125DF410) yet, but it looks like Digikey just got some. We might be able to build a few boards with them soon.

The 10G retimer also has a big GND pad underneath it so you would need to be comfortable with hot air rework to remove it.

I have not tried the 2.5G mode on the GPON SFPs yet. The Source Photonics GPON SFPs (branded as Alcatel/Nokia and FS.com) also require an update to the board microcontroller to function properly.

Ah, hot air rework might be a bit beyond my capabilities… Though given the part reference and the board I figure some repair shop here in San Francisco might be able to help me out? I’d certainly love to be able to use the GPON SFP directly without the intermediary 2.5-to-10G switch. :slight_smile:

I’ve ordered one of these DFP-34X-2C2 GPON SFPs based on some of the information discussed in this repo. It’s capable of running at 1G and multiple 2.5G modes, so hopefully if the retimer is the only issue, it may be compatible.