I got this answer from ChatGPT.
Yes, it is possible to create a single tun device that handles a range of IP addresses in Linux. This can be achieved by using the tunctl command to create a tun device and then configuring it with the appropriate IP address range.
Here are the steps to create a single tun device that handles a range of IP addresses:
Install the uml-utilities package if it is not already installed.
This package contains the tunctl command that we will use to create the tun device.
sudo apt-get install uml-utilities
Use the tunctl command to create a new tun device. In this example, we will create a tun device named tun0.
sudo tunctl -t tun0
Assign an IP address to the tun device using the ifconfig command.
In this example, we will assign the IP address range of 10.0.0.0/24 to the tun device.
sudo ifconfig tun0 10.0.0.1 netmask 255.255.255.0 up
Enable IP forwarding on the server using the sysctl command.
This will allow the server to forward traffic between the tun device and the eth0 interface.
sudo sysctl -w net.ipv4.ip_forward=1
Configure the routing table to route traffic from the tun device to the eth0 interface. In this example, we will use the route command to add a route for the 10.0.0.0/24 network.
sudo route add -net 10.0.0.0 netmask 255.255.255.0 dev tun0
sudo route add -net 10.0.0.0 netmask 255.255.255.0 gw <eth0_ip_address>
By following these steps, you can create a single tun device that handles multiple IP address ranges in Linux. This can be useful for managing a large number of users on a server without having to create a separate tun device for each user.
