2.5Gb/s performance at 1Gb/s rate
2.5Gb/s performance at 1Gb/s rate
Hi, I recently chose Linux for my primary operating system and have encountered some issues with my network interface cards. My configuration is quite simple: two 2.5Gb/s NICs, one on my PC and the other on my server, both connected directly to each other. The issue is that I can't achieve the advertised speeds in Linux. I'm using Kubuntu 21.04, and I haven't experienced this problem before on Windows. I have the R8125 driver installed and enabled, but it doesn't resolve the matter. When I run "ehtool enp9s0," the output shows:
Settings for enp9s0:
Supported ports: [TP]
Supported link modes: 10baseT/Half, 10baseT/Full, 100baseT/Half, 100baseT/Full, 1000baseT/Full
Advertised 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
Link partner advertised pause frame use: Symmetric Receive-only
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 1000Mb/s (Duplex: Full)
Auto-negotiation: On
Port: Twisted Pair PHYAD: 0
Transceiver: internal MDI-X: Unknown
Wake-on: pumbg
Current message level: 0x00000033 (51)
It seems the hardware is functional and supports negotiation, but the speed remains stuck at 100Mb/s. Since I didn't purchase both cards expecting slower performance like an integrated Ethernet card, your setup appears to be working well under Windows. Could there be a configuration mismatch or driver issue? It would help if you could share more details about your cable type and any recent changes.
It appears the setup functioned on Windows, but a different Ethernet cable might be needed. Also review the settings under Configure Network Connections when you right-click the network icon in the system tray. Network Manager behaves oddly and can misconfigure link negotiation. Interestingly, it’s set to Ignore, yet it works properly—consider switching between Automatic, Ignore, or Manual modes to test if it affects performance.
Hey, I tried a different cable that seemed reliable, but it didn’t make a difference. In Network Manager it’s set to auto and still doesn’t reach 10Gb/s in ignore or manual mode. There was a speed reading of 2500Mb/s at setup, then dropped to 1000Mb/s once connected. It’s confusing—I’m not sure what’s stopping me from fully wiping Windows yet.
Are you using the official Realteks driver or stock Linux support? It seems unusual since most discussions focus on Windows networking problems where Linux works well. What I lack is a Realtek 2.5Gbit PCIe NIC. I have USB 2.5Gbit, a 5Gbit Aquantia, a few 10Gbit Aquantias, and an Intel 10Gbit in the server—all functioning perfectly in Linux despite the Realtek taking longer to boot, which causes my NFS mounts to fail. Generally, I’d steer clear of Realtek hardware, as it’s often low-quality. Unfortunately, I’m a bit too late to heed that suggestion.
It's the official Realtek driver, downloaded directly from their site. Mostly I run into issues at full speed, but they're providing real performance rather than just 1000Mb/s. I'm considering switching distros or trying a live boot to check, since my Ubuntu Server 20.04 doesn't have the same problems as my main PC.
It seems the driver works with Linux kernels up to 5.6, but your system is 5.11. That might cause issues since the supported version isn’t fully compatible.