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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

[Hardware Failure] Cannot set ethernet connection to gigabit speeds

My ethernet connection seems to be stuck at 100Mbps, despite my board supporting 2.5Gbps, using all cat5e or cat6 cables, and a router that provides gigabit connection to multiple other devices. I have tried setting it with ethtool, which only makes the link go down and doesn't fix anything. I have tried swapping all kinds of cables, and connecting to different ports on the router and on the network switch. Everything I have found online implies a cable issue, but I have tried every cable under the sun, including ones that have worked at gigabit speeds with other devices. I'm rather stumped, and hoping against hope it's not a motherboard issue.

Output of "ethtool enp39s0":

Settings for enp39s0:
	Supported ports: [ TP	MII ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                       100baseT/Half 100baseT/Full
	                       1000baseT/Full
	                       2500baseT/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
	                       2500baseT/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/Half 1000baseT/Full
	Link partner advertised pause frame use: Symmetric Receive-only
	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
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: Unknown
netlink error: Operation not permitted
	Link detected: yes

Output of "ethtool enp39s0" after running "sudo ethtool -s enp39s0 speed 1000 duplex full autoneg on":

Settings for enp39s0:
	Supported ports: [ TP	MII ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                       100baseT/Half 100baseT/Full
	                       1000baseT/Full
	                       2500baseT/Full
	Supported pause frame use: Symmetric Receive-only
	Supports auto-negotiation: Yes
	Supported FEC modes: Not reported
	Advertised link modes:  1000baseT/Full
	Advertised pause frame use: Symmetric Receive-only
	Advertised auto-negotiation: Yes
	Advertised FEC modes: Not reported
	Speed: Unknown!
	Duplex: Unknown! (255)
	Auto-negotiation: on
	master-slave cfg: preferred slave
	master-slave status: unknown
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: Unknown
netlink error: Operation not permitted
	Link detected: no

Output of "sudo dmesg | grep r8169":

[    3.912817] r8169 0000:27:00.0: enabling device (0000 -> 0003)
[    3.919722] r8169 0000:27:00.0 eth0: RTL8125A, 2c:f0:5d:10:00:0b, XID 609, IRQ 81
[    3.919729] r8169 0000:27:00.0 eth0: jumbo features [frames: 9194 bytes, tx checksumming: ko]
[    3.936778] r8169 0000:27:00.0 enp39s0: renamed from eth0
[    5.329249] Realtek Internal NBASE-T PHY r8169-0-2700:00: attached PHY driver (mii_bus:phy_addr=r8169-0-2700:00, irq=MAC)
[    5.461415] r8169 0000:27:00.0 enp39s0: Link is Down
[   35.416291] Realtek Internal NBASE-T PHY r8169-0-2700:00: Downshift occurred from negotiated speed 1Gbps to actual speed 100Mbps, check cabling!
[   35.416319] r8169 0000:27:00.0 enp39s0: Link is Up - 100Mbps/Full (downshifted) - flow control rx/tx
[  853.288083] r8169 0000:27:00.0 enp39s0: Link is Down

Yes, I know it says "check cabling". I have.

Output of "nmcli connection up 'Wired connection 1'" after trying to change speed with ethtool:

Error: Connection activation failed: No suitable device found for this connection (device enp39s0 not available because device has no carrier).

Any help would be greatly appreciated!

Last edited by TheLastTeapot (2025-05-04 05:51:18)

mackin_cheese

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Registered: 2025-01-07

Posts: 475

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

boot into a liveUSB and see if it's picking up 1000 or 100

TheLastTeapot

Member

Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

That is a good idea, I hadn't thought of that. Unfortunately the result is the same.

https://i.ibb.co/VYw15ckD/Live-Iso-Output.jpg

Last edited by TheLastTeapot (2025-04-14 10:23:28)

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

Please replace the oversized image w/ a link.
Instead of the install iso w/ likely similar-ish kernel, try eg. https://grml.org/

Then remember that plugs and jacks are part of the cable, on both ends!
If you can still wiggle an rj45 connector, it's not properly slotted.

That being said:
https://bbs.archlinux.org/viewtopic.php?id=304219
https://bbs.archlinux.org/viewtopic.php?id=304570
https://bbs.archlinux.org/viewtopic.php … 6#p2232136

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TheLastTeapot

Member

Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I have heard before that some Realek adapters are more picky than other brands, hearing it again gives me hope. I have downloaded grml and am working on manufacturing a cat6 cable to connect directly to the router. Thank you for your help, I will update you.

TheLastTeapot

Member

Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

No luck. I booted into grml, connected directly to the router with a cat6 ethernet cable I just terminated myself. Same result from ethtool and dmesg:

https://i.ibb.co/N6ytbqRP/20250414-133616.jpg

seth

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Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

Can you test it against a different peer?

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I have tested it with two gigabit laptops, one windows and one linux, and I know the windows one has a realtek adapter. Both got a gigabit connection with no difficulty.

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I meant the affected system against a different routerswitchmodem resp. at least a different slot on the presently used one.

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I don't have another router or modem to test against, but I do have a gigabit switch. I actually get some interesting behavior here. When connected to the router, either port, ethtool lists 1000Mbps as the advertised speed, it autonegotiates 1000Mbps, and then fails. But when connected to the switch, any port, ethtool lists 100Mbps as the advertised speed, and it doesn't even try to reach gigabit. I wonder if this has something to do with the switch detecting that my computer won't get gigabit, and setting it  to 100Mb instead. For the record, other devices can get gigabit speeds through the switch, on the same ports I have tested my computer on.

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

Assuming the plug is firmly seated and does not rattle and you cannot wiggle it: how long is the cable?
(Your host advertises 1000Mbit/s - the switch might just be more aggressive about "yeah, that signal won't do gigabit" where the router just goes w/ the advertisements and downshifts later)

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-thc

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Registered: 2017-03-15

Posts: 998

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

working on manufacturing a cat6 cable to connect directly to the router

a cat6 ethernet cable I just terminated myself

Are you crimping the cables yourself?

Have you tried a manufactured patch cable instead?

TheLastTeapot

Member

Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

working on manufacturing a cat6 cable to connect directly to the router

a cat6 ethernet cable I just terminated myself

Are you crimping the cables yourself?

Have you tried a manufactured patch cable instead?

Allow me to explain my network setup. I have a router/modem, which has two gigabit ethernet ports. Since we need more than that, one of those ports goes to a gigabit ethernet switch, which has several devices connected. All those cables go to a patch panel in the wall behind the router/modem. The patch panels are all wired with cat5e ethernet cable. One of those lines goes to a room with a different, working gigabit laptop. Another goes to the room with my pc, which is closer than the other. So when I am connected to the switch, the path is:
Modem-cat5e-switch-cat5e-patch panel-cat5e-other patch panel-cat5e/cat6-pc
When I am connected directly to the modem, the path is:
Modem-cat5e-panel-cat5e-panel-cat5e/cat6-pc

With that setup, I have tried an assortment of cat5e and cat6 cables going from the nearest patch panel to my pc. Homemade, the one that came with the router, a cat6 one we bought, and an assortment of other cat5e cables of unknown origin. When that failed, I lugged my pc into the room with the router, and retried all those same cables connected directly to the router, with the exception of the storebought cat6 cable, because it is too short (1ft/30cm). I can test that one directly to the router, if you're really sure it will help.

When that failed, yesterday my brother and I pulled out his spool of shielded cat6 cable, cut a ~20-30 foot section, crimped it with new connectors, and ran it through the wall, which means that now, instead of the whole complicated setup, I have a direct high quality cat6 link to the router/modem, no patch panels or other connections between, no more than 30 feet long, and in all likelihood closer to 20. I can't measure now, because it's in the wall.
That gave me no different results than the complicated cat5e setup.

Assuming the plug is firmly seated and does not rattle and you cannot wiggle it: how long is the cable?

It wiggles a little, does not rattle. It is about 25 feet long, heavy duty shielded cat6. Here is a video of the wiggling:
https://drive.google.com/file/d/19YkKz4 … p=drivesdk

TL; DR: Yes I crimped it myself. Yes I have tried other cables. It's about 25 feet long.
It doesn't rattle, it does wiggle a little. Here's a video, no idea if it's within tolerance or not. All 8 pins inside the port are present and coreect, none appear to be damaged, bent, or stuck in any way.

seth

Member

From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

lugged my pc into the room with the router, and retried … the one that came with the router

And the amount of wiggling is fine (it's plastic after all, but doesn't move inside the slot)

Do you get a better signal w/ https://aur.archlinux.org/packages/r8125-dkms ?

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I will test that tomorrow, today I am away from home all day

TheLastTeapot

Member

Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

sudo ethtool enp39s0

gives:

Settings for enp39s0:
	Supported ports: [ TP ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                       100baseT/Half 100baseT/Full
	                       1000baseT/Full
	                       2500baseT/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
	                       2500baseT/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/Half 1000baseT/Full
	Link partner advertised pause frame use: Symmetric Receive-only
	Link partner advertised auto-negotiation: Yes
	Link partner advertised FEC modes: Not reported
	Speed: 100Mb/s
	Duplex: Full
	Auto-negotiation: on
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: on
	Supports Wake-on: pumbg
	Wake-on: g
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
	Link detected: yes

 sudo dmesg | grep r8125

gives:

[    3.837620] r8125 Ethernet controller driver 9.015.00-NAPI loaded
[    3.837671] r8125 0000:27:00.0: enabling device (0000 -> 0003)
[    3.860435] r8125: This product is covered by one or more of the following patents: US6,570,884, US6,115,776, and US6,327,625.
[    3.860511] r8125  Copyright (C) 2024 Realtek NIC software team <nicfae@realtek.com> 
[    3.874843] r8125 0000:27:00.0 enp39s0: renamed from eth0
[   20.754170] r8125: enp39s0: link up

Still at 100Mbps, but this time it didn't even autonegotiate.  Setting it to 1Gbps has the same result as before. It looks like "Supported ports" has lost MII, and now only has TP. I don't know what those are and if that matters.

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

https://github.com/aravance/r8125/
Apparently the module allows you to force the speed=1000 … see what that gets you (transmission errors?)

https://serverfault.com/questions/56622 … ir-is-used - that's fine

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

I am having no success forcing the speed, with the aur version or the git version. It simply has the same result as trying to set with ethtool did before. I assume the instructions in the readme are what I need to follow to force the settings? Trying to force with ethtool had the same result as before, and trying to force it when loading the module also had no effect, but in dmesg it said "unknown parameter 'speed' ignored" "unknown parameter 'duplex' ignored" "unknown parameter 'autoneg' ignored". Am I missing sonething?

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

systool -vm r8125

Booting w/ "r8125.speed=1000" should™ enforce it.

Edit: there seems some "speed_mode" parameter.

Last edited by seth (2025-04-17 15:03:59)

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

Booting w/ "r8125.speed=1000" should™ enforce it.

As a kernel parameter?

Sorry about the delay, these last couple days got crazy

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

Yup, but from looking up the code test the speed_mode parameter and post the "systool -vm 8125" output (it'll hopefully list all set parameters, "modinfo r8125" might as well show the available ones)

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

modinfo r8125:

filename:       /lib/modules/6.14.2-arch1-1/kernel/drivers/net/ethernet/realtek/r8125.ko.zst
version:        9.015.00-NAPI
license:        GPL
description:    Realtek r8125 Ethernet controller driver
author:         Realtek and the Linux r8125 crew <netdev@vger.kernel.org>
srcversion:     FBFD27B273C12494CC52E86
alias:          pci:v000010ECd00003000sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008162sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008125sv*sd*bc*sc*i*
depends:        
name:           r8125
retpoline:      Y
vermagic:       6.14.2-arch1-1 SMP preempt mod_unload 
parm:           speed_mode:force phy operation. Deprecated by ethtool (8). (uint)
parm:           duplex_mode:force phy operation. Deprecated by ethtool (8). (uint)
parm:           autoneg_mode:force phy operation. Deprecated by ethtool (8). (uint)
parm:           aspm:Enable ASPM. (int)
parm:           s5wol:Enable Shutdown Wake On Lan. (int)
parm:           s5_keep_curr_mac:Enable Shutdown Keep Current MAC Address. (int)
parm:           use_dac:Enable PCI DAC. Unsafe on 32 bit PCI slot. (int)
parm:           timer_count:Timer Interrupt Interval. (int)
parm:           eee_enable:Enable Energy Efficient Ethernet. (int)
parm:           hwoptimize:Enable HW optimization function. (ulong)
parm:           s0_magic_packet:Enable S0 Magic Packet. (int)
parm:           tx_no_close_enable:Enable TX No Close. (int)
parm:           enable_ptp_master_mode:Enable PTP Master Mode. (int)
parm:           disable_wol_support:Disable PM support. (int)
parm:           enable_double_vlan:Enable Double VLAN. (int)
parm:           eee_giga_lite:Enable Giga Lite. (int)
parm:           debug:Debug verbosity level (0=none, ..., 16=all) (int)

Booting with r8125.speed_mode=1000 has almost the same result. When I booted up ethtool looked the same as after trying to set the speed, with  the speed and duplex listed as "Unknown!"

Settings for enp39s0:
	Supported ports: [ TP ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                       100baseT/Half 100baseT/Full
	                       1000baseT/Full
	                       2500baseT/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: No
	Advertised auto-negotiation: Yes
	Advertised FEC modes: Not reported
	Speed: Unknown!
	Duplex: Unknown! (255)
	Auto-negotiation: on
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: Unknown
netlink error: Operation not permitted
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
	Link detected: no

The major difference is that this time running "nmcli connection up 'Wired Connection 1'" actually had an effect. It didn't set the speed to 1000, but it produced this state in ethtool:

Settings for enp39s0:
	Supported ports: [ TP ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                       100baseT/Half 100baseT/Full
	                       1000baseT/Full
	                       2500baseT/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/Half 1000baseT/Full
	Link partner advertised pause frame use: Symmetric Receive-only
	Link partner advertised auto-negotiation: Yes
	Link partner advertised FEC modes: Not reported
	Speed: 100Mb/s
	Duplex: Full
	Auto-negotiation: on
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: on
netlink error: Operation not permitted
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
	Link detected: yes

When I disabled all other internet connections and tried to pull up the browser to open internet speed test, at first the pages loaded, just very slowly. But after a minute they would not load at all, and after that point I couldn't get anything to load. Ethtool still had that same output as after setting the connection up with nmcli.

Also, I don't have systool. What package does that come with?

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

sysfsutils - let's try something different: return to the in-tree driver, stock config, no special parameters - except: disable the duplex mode.
Does it still downshift or can you run 100Mbit half-duplex?

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TheLastTeapot

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Registered: 2022-11-25

Posts: 25

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

100Mbit half duplex or 1000Mbit half duplex?

Last edited by TheLastTeapot (2025-04-23 00:13:00)

seth

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From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 69,217

Re: [Hardware Failure] Cannot set ethernet connection to gigabit speeds

1000Mbit half duplex
The theory would be that duplex doesn't properly work what causes (too much) noise what then causes the downshift, so half-duplex might go (slightly slower but) uninterfered at 1000 Mbit/s

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