Unable to get 1gbps on Realtek 2.5 GbE NIC

truncs · 2023-03-27 03:47:28

I have a a Realtek 2.5GbE NIC which is unable to get 1gbps. I am using the r8125-dkms driver from AUR. It's a bit puzzling since I am using a CAT 7 ethernet cable and my previous Intel NIC was able to easily get 1 gbps.

04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller (rev 05)
	Subsystem: Gigabyte Technology Co., Ltd Device e000
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 18
	Region 0: I/O ports at 4000 [size=256]
	Region 2: Memory at 75300000 (64-bit, non-prefetchable) [size=64K]
	Region 4: Memory at 75310000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: <access denied>
	Kernel driver in use: r8125
	Kernel modules: r8169, r8125

When setting using ethtool, the NIC is unable to get an ip address and fails to connect to the internet.

sudo ethtool -s enp4s0 speed 1000 duplex full autoneg off

I can see in modinfo that it does provide these speeds

$ modinfo r8125
filename:       /lib/modules/6.2.8-arch1-1/updates/dkms/r8125.ko.zst
version:        9.011.00-NAPI
license:        GPL
description:    Realtek RTL8125 2.5Gigabit Ethernet driver
author:         Realtek and the Linux r8125 crew <netdev@vger.kernel.org>
srcversion:     CBDA9F0B8BED66BA59DD3EB
alias:          pci:v000010ECd00005000sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008126sv*sd*bc*sc*i*
alias:          pci:v000010ECd00003000sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008162sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008125sv*sd*bc*sc*i*
depends:        
retpoline:      Y
name:           r8125
vermagic:       6.2.8-arch1-1 SMP preempt mod_unload 
sig_id:         PKCS#7
signer:         DKMS module signing key
sig_key:        2F:76:71:B7:24:87:18:44:59:FD:22:6D:FA:DE:46:FA:66:72:6F:23
sig_hashalgo:   sha512
signature:      76:7C:99:EF:18:7F:ED:14:94:86:14:B0:A3:BC:FA:8A:8E:96:01:4B:
		30:2D:DC:A0:E0:39:8C:CE:BF:2F:4C:F4:A7:97:73:C7:E4:4B:F8:D4:
		45:9D:23:D0:89:C2:AD:73:52:7F:FE:C0:68:B7:87:D8:3D:E3:5E:31:
		F4:07:CC:0F:E6:0A:F2:B3:A1:F3:72:00:15:8B:8F:39:F9:00:05:9A:
		9C:DD:0C:D4:6F:00:5F:7B:B6:ED:3D:29:17:6E:BC:25:BE:16:9A:B1:
		09:6A:E0:69:58:34:11:7F:AA:77:E8:00:8A:C6:82:D1:82:1A:EB:4E:
		7E:FB:2F:9A:72:AE:1C:86:50:1A:06:40:81:62:3A:40:78:4A:55:CD:
		D9:57:2B:76:AC:76:A8:8F:BE:13:F8:DF:E5:A2:05:D3:3E:10:9A:1F:
		7E:FF:D0:F1:D4:64:BC:F4:4B:4E:68:80:DB:16:4F:9F:99:12:A9:51:
		C9:8F:7A:76:86:F3:19:DE:DF:16:1D:91:4C:3B:51:7E:02:A7:88:8D:
		13:18:C2:83:64:7B:FF:B5:7B:1A:0C:DB:3D:C1:0B:5D:8E:27:B2:26:
		8C:08:32:26:6B:6A:E8:7C:08:27:44:81:67:EB:B5:81:6D:C6:DE:59:
		F5:6A:BD:E4:D0:E4:E5:51:D2:5C:FD:F7:EC:17:72:83
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:           advertising_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_pm_support:Disable PM support. (int)
parm:           enable_double_vlan:Enable Double VLAN. (int)
parm:           debug:Debug verbosity level (0=none, ..., 16=all) (int)

I am using the following kernel

Linux earth 6.2.8-arch1-1 #1 SMP PREEMPT_DYNAMIC Wed, 22 Mar 2023 22:52:35 +0000 x86_64 GNU/Linux

orlfman · 2023-03-27 03:50:22

any reason why you are using the AUR driver? correct me if i'm wrong but i thought the r8125 support was mainlined into the kernel? i thought the out of tree driver was prior before the kernel received proper support for it.

Last edited by orlfman (2023-03-27 03:50:59)

truncs · 2023-04-13 01:47:19

I suppose that would be r8168/r8169? That had the same problem.

truncs · 2023-05-05 16:03:29

Got a Intel NIC and that gives 1 Gbps, seems like the best way to go instead of dealing with Realtek driver issues.

grail69 · 2025-07-12 10:32:23

I realise this was a few years ago, but I am having the exact same issue in that my Realtek RTL8125 2.5GbE is only running at 100MB after installing the r8125-dkms.

I am also unable to run the following at all:

sudo ethtool -s enp4s0 speed 2500 duplex full autoneg off
netlink error: link settings update failed
netlink error: Invalid argument

Any suggestions are greatly appreciated?

seth · 2025-07-12 14:41:00

What's actually there?

ethtool enp4s0

Arch Linux

#1 2023-03-27 03:47:28

Unable to get 1gbps on Realtek 2.5 GbE NIC

#2 2023-03-27 03:50:22

Re: Unable to get 1gbps on Realtek 2.5 GbE NIC

#3 2023-04-13 01:47:19

Re: Unable to get 1gbps on Realtek 2.5 GbE NIC

#4 2023-05-05 16:03:29

Re: Unable to get 1gbps on Realtek 2.5 GbE NIC

#5 2025-07-12 10:32:23

Re: Unable to get 1gbps on Realtek 2.5 GbE NIC

#6 2025-07-12 14:41:00

Re: Unable to get 1gbps on Realtek 2.5 GbE NIC

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