Ethernet Connection Negotiating at 100M/Full Despite Switch Being Capable of Gigabit

[rjdipcord]

Hey all,

 

Strange issue that's been plaguing me ever since I began using the internal NIC on my unraid server. The link between it and the switch is always 100M Full-duplex despite the switch being capable of gigabit. I am using a Unifi USW-24-250W switch and I have checked the port configuration. It is set to auto-negotiate. That would seem to be true as when I run ethtool, I can see that the advertised link modes includes 1000M.
 

Settings for eth0:
        Supported ports: [ TP    MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Full
        Link partner advertised pause frame use: No
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 100Mb/s
        Duplex: Full
        Auto-negotiation: on
        master-slave cfg: preferred slave
        master-slave status: slave
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: external
        MDI-X: Unknown
        Supports Wake-on: pumbg
        Wake-on: d
        Link detected: yes

 

The cable is fine. I was able to check continuity and all 4 pairs are in good health. Tried using 3 other cables just in case but found no success.

 

Even if I force the connection to be gigabit through the port config on the switch, the connection drops completely and will not come back online until I put it back on auto, or otherwise set it to force 100M.

[nerbonne]

Not an expert by any means, but i'd imagine that we'd need info on the motherboard/nic model to help.  Posting the diagnostics is what JorgeB is gonnna say anyways, just saving him the trouble.

[JonathanM]

This can also happen if a pin is bent in the socket. Try taking a photo of the socket and zooming in to see if all 8 pins look identical.

[rjdipcord]

Aright, here's my diagnostics.

 

And I took a look at the port on the MB and the port on the switch. Both seem to be in great shape.

 

 

 

The MB is an MSI X470 GAMING PLUS MAX. and it has a Realtek® 8111H Gigabit LAN controller.

lilnas-x-diagnostics-20230328-1247.zip

[JorgeB]

Try using a known good port on the switch, one that's linking a gigabit speeds, if that doesn't do it and if you already tried different cables it's likely a NIC problem.

[rjdipcord]

4 hours ago, JorgeB said:

Try using a known good port on the switch, one that's linking a gigabit speeds, if that doesn't do it and if you already tried different cables it's likely a NIC problem.

Yeah literally tried that right as I took the photo I attached. Port 12 is where the NAS was connected prior. Port 10 is where I moved it to while I took the photo. And you can see by the orange light, it's also negotiating at 100M.

[itimpi]

Have you actually tried a different cable?    It only takes one of the wires in a cable to be faulty for the link speed to downgrade to 100Mb

[rjdipcord]

Alright, I absolutely have no idea what's going on.

I went and ran

Quote

dmesg | grep r8169

r8169 is the realtek driver for my NIC.

This spat out a few interesting errors that would point to a bad cable:

Quote

[1211831.427407] Generic FE-GE Realtek PHY r8169-0-2200:00: Downshift occurred from negotiated speed 1Gbps to actual speed 100Mbps, check cabling!
[1211831.427427] r8169 0000:22:00.0 eth0: Link is Up - 100Mbps/Full (downshifted) - flow control off

Okay, so I have already tried different cables to no avail. I even tried a cat6A cable just in case. Still nothing.

So instead of plugging into the switch, I plugged into my Dream Machine Pro. BOOM - gigabit. Great! the network switch was the problem! Perhaps not. Because I then took the cable (the original one) and plugged it back into the switch on the same port it normally is patched to. Still gigabit.

 

So truthfully. No idea what's going on here. It makes no sense for what I did to troubleshoot fixed the problem imo. But I will still mark itimpi's suggestion as a solution because that is what made me think to change ports from the switch to the UDMP.