Enabling full potential of USB (Realtek) Nic 2.5Gbe on debian

Let's allow debian to maximize Realtek's R8152's performance.

I am a big fan of Linux (especially Debian-based distros), and I am also passionate about maximizing network speeds.Even after upgrading my network to 2.5Gbit (and my backbone to 10Gbit), my Linux Hypervisor (running Proxmox - more on that later) failed to run full duplex from one of its USB ports.

At first, you check if the driver is correcty loaded anyhow:

dmesg | grep enx

When the driver isn't correctly loaded, the output will be something like:

cdc_ncm 5-2:2.0 enxXXXXXXXX: renamed from eth0

cdc_ncm indicates that the realtek drivers (in my case r8152) are not loaded, affecting network properties (running in half-duplex mode, for example) and resulting in subpar performance.

The solution

The solution is actually very straightforward; you just need to tell your system to load these drivers by default by creating a .rules file in udev. Be sure to place the contents of https://github.com/bb-qq/r8152/blob/master/50-usb-realtek-net.rules in /etc/udev/rules.d/50-usb-realtek-net.rules.

💡

Easy way of getting the file content on your disk is by executing the two lines below as follows:

wget https://raw.githubusercontent.com/bb-qq/r8152/master/50-usb-realtek-net.rules
mv 50-usb-realtek-net.rules /etc/udev/rules.d/50-usb-realtek-net.rules

Give the system a reboot and then you start over again by dmesg | grep enx, and check the output. If it shows something like:

r8152 6-2:1.0 enxXXXXXXXX: renamed from eth0

then it means you are good to go - the drivers are correctly loaded, allowing full usage of the 2.5GBit nic.