How can I limit link speed on Ubuntu server 20.04

OS:Ubuntu 20.04 server - Virtualbox Interface: enp0s3

I've been looking ofr a solution to limit link speed to 10Mb/s, half duplex and autonegotiation disabled. As I saw on the [link][1] guide but it doesn't work. When I do a networkctl status enp0s3, it just shows autonegotiation on, speed 1Gs and Duplex full. And that never changes, even if it shows it's taking the configuration from my file. Then I discovered the systemctl status systemd-udevd command to get more information about the issue and I found this error:

I need to create a file inside /etc/systemd/network/ that's called 10-mb.link to apply the following configuration:

[MATCH]

MACAddress=ex:am:pl:e0:ma:c1

[LINK]

BitsPerSecond=10M

Duplex=Half

I followed these instructions: [1]: https://manpages.ubuntu.com/manpages/focal/man5/systemd.link.5.html and [2]: https://linuxiac.com/how-to-manipulate-ethernet-card-on-linux-with-ethtool-command/

But none worked, I don't know what else to try, my testing system doesn't have NetworkManager (which I read could be causing issues, but it's not even installed)

Also, on the physical devices I've been able to set configuration I said above on, but as soon as we boot, they lose what's been configured. I did it using this command: "ethtool -s enp2s0 speed 10 duplex half autoneg on" but it doesn't work on the virtual machine, my system just forgets about it after booting up, so my question is, how can I make this changes permanent?

You can add that command as a cronjob using sudo crontab -e then add a line to run the command after each boot like this:

@reboot sleep 30 && ethtool -s enp2s0 speed 10 duplex half autoneg on

The sleep 30 will delay the execution of the command for 30 seconds after boot to allow the interface to come up first … You can decrease or increase the delay as you need.

Alternatively, you can use different methods to achieve some or all the results you want … For example, you can use traffic shaping rules using only tc to limit the bandwidth rate ... I copied mine and modified it eliminating irrelevant rules and changing the numbers to match your requirement ... It should limit download and upload to 10 Mbit/second ... Copy/paste and execute all commands one at a time:

sudo tc qdisc add dev wlp2s0 root handle 1: cbq avpkt 1000 bandwidth 10mbit
sudo tc class add dev wlp2s0 parent 1: classid 1:1 cbq rate 10000kbit allot 1500 prio 5 bounded isolated
sudo tc class add dev wlp2s0 parent 1:1 classid 1:10 cbq rate 10000kbit allot 1600 prio 1 avpkt 1000
sudo tc class add dev wlp2s0 parent 1:1 classid 1:20 cbq rate 10000kbit allot 1600 prio 2 avpkt 1000
sudo tc qdisc add dev wlp2s0 parent 1:10 handle 10: sfq perturb 10
sudo tc qdisc add dev wlp2s0 parent 1:20 handle 20: sfq perturb 10
sudo tc filter add dev wlp2s0 parent 1:0 protocol ip prio 10 u32 match ip tos 0x10 0xff  flowid 1:10
sudo tc filter add dev wlp2s0 parent 1:0 protocol ip prio 11 u32 match ip protocol 1 0xff flowid 1:10
sudo tc filter add dev wlp2s0 parent 1: protocol ip prio 13 u32 match ip dst 0.0.0.0/0 flowid 1:20
sudo tc qdisc add dev wlp2s0 handle ffff: ingress
sudo tc filter add dev wlp2s0 parent ffff: protocol ip prio 50 u32 match ip src 0.0.0.0/0 police rate 10000kbit burst 1000kbit drop flowid :1

You need to change wlp2s0 to the name of your interface.

You should read the documentation first, but if you get stuck with 10 Mbit/s and don't know how to go back, this should bring you back:

sudo tc qdisc del dev wlp2s0 handle ffff: ingress
sudo tc qdisc del dev wlp2s0 root

Change wlp2s0 to the name of your interface here as well.