10/100/1000Mbps Autonegotiation for SFP+ ports configured as 1G?

Hi,

I am currently using 1G copper SFPs (Fiberworks SFP-1000Base-TX) supporting 10/100/1000Mbps for ports 9 and 10. This choice was made in favor of a 10G SFP because the 1G version meets my data rate requirements, generates less heat, and is cheaper.

I’m curious to know if autonegotiation for SFP+ ports 9 & 10, configured as 1G, will be implemented in the future for the UbiSwitch (with baseboard), similar to the existing functionality on ports 1-8.

As of know, I can only connect devices compatible with data rates of 1G to ports 9 and 10 with this configuration.

That’s a valid rationale for choosing a 1G over a 10G SFP module.

When dealing with SFP modules, there are essentially two levels of autonegotiation going on so let’s first clarify terminology.

PHY Level auto-negotiation refers to the auto-negotiation between two physical layer devices. This is the auto-negotiation we are all familiar with whether two RJ-45 ports connected together will auto-negotiate to the fastest speed possible. In your case, the auto-negotiation is between the SFP module’s RJ-45 port, and the device you connect to the SFP with the RJ-45 cable.

MAC Level auto-negotiation refers to the auto-negotiation between two MAC devices. In this case this is the “backplane speed” between the gold fingers on the SFP module, and the MAC port on UbiSwitch. In the case of UbiSwitch, you manually set this to either USXGMII for 10Gbps, or SGMII for 1Gbps. Changing the jumper as outlined in the forum post below toggles between those two modes.

MAC level auto-negotiation has no effect on PHY level auto-negotiation. For example, you can connect a 10G SFP to RJ45 to UbiSwitch, with the MAC backplane speed of USXGMII. That 10G SFP can still auto-negotiate down to 100Mbps, assuming the SFP’s PHY supports that. We’ve tested that, and it works. USXGMII doesn’t know (or care) about the PHY speed.

Likewise with a 1G SFP, and a MAC speed of SGMII, your SFP should also be able to auto-negotiate down to 10 or 100Mbps with the connected device (though we haven’t actually tested that).

With your ports 9 and 10 in SGMII mode, and your 1G SFP plugged in, have you tried connecting a 100Mbps device to the 1G SFP to see if the speed auto-negotiates down to 100Mbps?

Thanks for the informative reply!

Yes, I have tried connecting a few different 10/100Mbps devices to the 1G SFP, but have not been able to reach any of them.

FYI: Ports 9 & 10 were configured to SGMII mode by cutting jumper SM1.

Hmm, yeah that’s odd; Presumably the SFP works with a 1G device connected to it (to confirm that the SFP is plugged in correctly and getting power from UbiSwitch)?

Yes, it works fine when using a 1G device…

That’s a bit odd. Let’s debug :slight_smile:

In theory the MAC speed should have no effect on the PHY speed (other than limiting the maximum speed). Let’s debug where the issue here is; there are three things to check.

  1. Between the SFP module and the connected device
    Does the connected 100Mbps device successfully auto-negotiate a link with the SFP module? Do you see link lights on the device indicating it has a PHY link with the SFP? Can you query the device to see if the link is up? If no, then the issue is an auto-negotiation problem between the SFP and the connected device. If yes, move to 2.
  1. Between the SFP module and UbiSwitch
    With your device connected to the SFP module, and the SFP module connected to the UbiSwitch baseboard, connect another device like a computer to one of UbiSwitch’s 1G ports.
    Are you able to “ping” your connected device from the computer. If you don’t know how to do a ping test, a simpler way is to see if the LEDs on UbiSwitch flash together. If they consistently flash together, it means both devices can see each other.
    If there is an LED flashing for both the connected device and the computer, and they flash together, then both devices can see each other. If so then problem solved.
    If there is an LED flashing for both devices, but they do not flash together, then there is an issue with the network on UbiSwitch. If so move to 3.
    If there is only an LED for the computer, then UbiSwitch is not seeing the connected device through the SFP. If so then move to 3.

  2. Assuming you see lights on the connected 100Mbps device, but either no corresponding LED on Ubiswitch (or an LED that does light up but not blink in sync with the other LED), can you repeat this test with a 1000Mbps connected device and let me know what you see on UbiSwitch?