TP-Link Archer C6 v3 Linkspeed negotiation woes

[OpenWrt Bugs]

Hi All,

Please feel free to send me to /dev/null if this has been reported, I 
could not find any reports on the bug tracker.

I have an issue on my tp-link archer C6 v3 running OpenWrt SNAPSHOT, 
r18711-4367d4f869,

I get my internet from a wisp, meaning my uplink is connected to my 
OpenWrt through a POE, the issue I am experiencing is when I attempt to 
autonegotiate a link to the CPE the link fails to establish.

My running theory is because both devices advertises 1000BaseT/Full the 
link tries to establish at 1Gbps however due to the POE being a 100Mbps 
device only, 1Gbps fails to establish and auto-negotiate does not 
attempt the lower negotiations.

I have tried to force the link to lower speeds, but unfortunately the 
only speeds I could semi-reliably get to work was 10baseT/Full. I say 
semi-reliably because after I started fiddling again it broke in such a 
way that a restart of the router was required.

As part of my troubleshooting I deployed an intermediate device between 
the CPE and the router that is only capable of 100baseT, which 
negotiated without any issues to both the CPE and the router. Replacing 
the intermediate device with a 1000baseT device also results in a 
successful negotiation to both ends (100M to the CPE, 1Gbps to the router)

Due to the router driving my internet and me working from home, I will 
only be able to test settings after hours so reply information could be 
delayed by up to 12 hours.

Kind regards
Ian Coetzee

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