Hi Björn,

On 22/02/2026 20:58, Björn Töpel wrote:

# # Simple MAC loopback:
# ethtool --set-loopback eth0 mac (Defaults: lanes=all, dir=near)
# # Specific SerDes (PMA) lane:
# ethtool --set-loopback eth0 pma:lane0
# # Complex multi-layer (PMA Near + PMD Far):
# ethtool --set-loopback eth0 pma:0x1:near pmd:all:far
# # Disable all loopbacks:
ethtool --set-loopback eth0 off

Thoughts? Is this somewhat close to what you had in mind, Andrew?

I'm far from an expert on the details here, so the folks with more
knowledge, please chime in!

I'm very sorry not to have looked into this yet, I'm having some family
events to handle right-now but I hope to be back next monday to take a
close look at this :)

Thanks for this work,

Maxime