The original workstation was changed to Ubuntu 24.04, and I usually need to connect to the workstation directly through my Windows office laptop. At first, I connected to the wireless network, but the upload and download data was too slow. Later, I used a wired network card to bridge, but sometimes the data was not transmitted through the wired network card but through the wireless network card. Disabling the laptop’s wireless network card and being unable to go online for work is not a good solution.

1. Temporary solution

The workstation is used as host A, the laptop is used as host B, and host B shares the wireless network of host A through a wired connection¹.

1.1 Query the current device network card

Query the network card hardware information of the two machines.

iwconfig

1.2 Configure a static IP for host A and use it as a soft router

It can be configured through the GUI, and host A only needs to set the IP address and subnet mask information.

sudo ifconfig eno1 192.168.68.1/24 # enol is the name of the wired network card connected to host A
ifconfig # 查询效果

1.3 Configure static IP, gateway and DNS for host B

This step can also be configured through the GUI. Host B needs to be configured with an IP address, subnet mask, and the gateway is set to the IP address of Host A. In addition, the DNS address needs to be set.

sudo ifconfig enp0s31f6 192.168.68.2/24 # enp0s31f6 is the name of the wired network card of host A
sudo route add -net 0.0.0.0/0 gw 192.168.68.1 # Add a Gateway
sudo chmod +666 /etc/resolv.conf 
sudo echo "nameserver 114.114.114.114" > /etc/resolv.conf # Add DNS

1.4 Enable IP forwarding

IP forwarding is disabled by default in Linux and needs to be enabled manually.

sudo bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'   # enable ip forwarding

1.5 Configuring NAT

Set up routing forwarding through iptables.

sudo iptables -F
sudo iptables -P INPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -t nat -A POSTROUTING -o wlp0s20f3 -j MASQUERADE     # wlp0s20f3 is the wireless network card that connects host A to the external network

This solution requires resetting 1.4 and 1.5 every time host A is restarted, which is very inconvenient.

2. Permanent solution

There are two options here. One is to write the command lines in 1.4 and 1.5 into a script and execute it automatically every time the computer is turned on. The other is to use iptables-persistent for persistent configuration². This article adopts the second method.

2.1 Install iptables-persistent

Execute the following command to install iptables-persistent.

sudo apt install iptables-persistent

2.2 Check the rules

Check the iptables rules that have been set³.

sudo iptables -L -t nat

2.3 Permanently enable IP forwarding

Edit the /etc/sysctl.conf file with administrator privileges⁴.

sudo vi /etc/sysctl.conf

Find this line, delete the comment symbol # in front of it, change the 0 after the equal sign to 1, save and exit.

#net.ipv4.ip_forward=1

2.4 Save iptables settings

After executing the command line in 1.5, run the netfilter-persistent save command as an administrator to permanently save the current iptables settings.

sudo netfilter-persistent save

Restart verification and the problem is solved.