# The SFP EEPROM appears to advertise only 10G optical-style host capabilities

**URL:** <https://forum.botblox.org/t/the-sfp-eeprom-appears-to-advertise-only-10g-optical-style-host-capabilities/606>\
**Category:** BotBlox Hardware\
**Tags:** sfp-10g-t\
**Created:** [July 2, 2026, 8:10pm UTC](https://forum.botblox.org/t/the-sfp-eeprom-appears-to-advertise-only-10g-optical-style-host-capabilities/606 "2026-07-02T20:10:45Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ameriane](https://avatars.discourse-cdn.com/v4/letter/a/87869e/32.png) [@ameriane](https://forum.botblox.org/u/ameriane)\
**Post date:** [July 2, 2026, 8:10pm UTC](https://forum.botblox.org/t/the-sfp-eeprom-appears-to-advertise-only-10g-optical-style-host-capabilities/606/1 "2026-07-02T20:10:45Z")

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We are using the SFP-10G-T on an NXP LX2160A platform.

The module successfully auto-negotiates with a 1G laptop and traffic passes correctly. However, the host always reports:

Port: FIBRE

Supported link modes: 10000baseSR/Full

Speed: 10000Mb/s

The SFP EEPROM also appears to advertise only 10G optical-style host capabilities. Is the SFP-10G-T designed to expose a fixed 10G host-side interface while performing copper-side auto-negotiation internally?

If so, is there any mechanism (MDIO, vendor-specific EEPROM page, diagnostics page, etc.) that allows a host system to retrieve the actual negotiated RJ45 speed (100M/1G/2.5G/5G/10G)?

Thank you.

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**Author:** ![josh\_elijah](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.botblox.org/josh_elijah/32/568_2.png) [@josh\_elijah](https://forum.botblox.org/u/josh_elijah)\
**Post date:** [July 4, 2026, 8:43pm UTC](https://forum.botblox.org/t/the-sfp-eeprom-appears-to-advertise-only-10g-optical-style-host-capabilities/606/2 "2026-07-04T20:43:23Z")

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Hi,

Yes, that behavior is expected for this class of 10GBASE-T SFP+ module.

The SFP-10G-T presents a fixed 10G host-side serial interface to the switch/MAC, while the internal copper PHY handles RJ45-side auto-negotiation independently. Because of that, the host reports the SFP port as a 10G fibre-style interface, for example 10000baseSR/Full or 10G full-duplex, even when the RJ45 side has negotiated 1G with the attached copper device.

The EEPROM advertisement reflects the host-side SFP+ interface rather than the copper-side link partner capability. This is normal for many 10GBASE-T SFP+ RJ45 modules and does not necessarily mean the copper side is running at 10G.

Regarding the actual negotiated RJ45 speed: there is no universal standards-based mechanism that all hosts can use to retrieve this from a 10GBASE-T SFP+ module.

Some modules expose copper-side status through vendor-specific I2C/EEPROM pages, diagnostics registers, or module-specific firmware behavior, but this is not guaranteed or portable across platforms. On many systems, ethtool will only show the host-side SFP+ link state, not the copper PHY’s negotiated RJ45 speed.

So in this case, the LX2160A reporting 10G/FIBRE while traffic passes correctly to a 1G laptop is consistent with the module operating as intended.

Best,

Josh

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**Author:** ![ameriane](https://avatars.discourse-cdn.com/v4/letter/a/87869e/32.png) [@ameriane](https://forum.botblox.org/u/ameriane)\
**Post date:** [July 6, 2026, 3:32pm UTC](https://forum.botblox.org/t/the-sfp-eeprom-appears-to-advertise-only-10g-optical-style-host-capabilities/606/3 "2026-07-06T15:32:37Z")

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Thanks for the answer.