===== ISC-DHCP-Server Installation =====

  * Run the following command to start the installation:

  sudo apt update
  sudo apt install isc-dhcp-server
 
   * You may check the DHCP version:

  dhcpd --version

   * Configure the network interfaces that the DHCP server will use by editing the config file:

  sudo nano /etc/default/isc-dhcp-server

  * For example, if your DHCP interface is tap_vpn, update the line as follows:

  INTERFACESv4="tap_vpn"

   * Configure the DHCP setting by editing the config file:

  sudo nano /etc/dhcp/dhcpd.conf

  * This part set the domain name and DNS servers:

  option domain-name "example.com";
  option domain-name-servers 8.8.8.8, 8.8.4.4;

  * This part set the subnet and IP address range:

  subnet 192.168.30.0 netmask 255.255.255.0 {
  range 192.168.30.100 192.168.30.200;
  option routers 192.168.30.1;
  }

   * Set the lease time:

  default-lease-time 600;
  max-lease-time 7200;

  * Assign IP address to the device before started the DHCP service (this is mandatory):

  sudo ip addr add 192.168.30.1/24 dev tap_vpn

  * Start the service:

  sudo systemctl start isc-dhcp-server
 
  * Enable the service:

  sudo systemctl enable isc-dhcp-server

  * Show the service status:

  sudo systemctl status isc-dhcp-server

==== Troubleshooting Common Issues ====

  * Check the DHCP server logs for any error messages:

  sudo tail -f /var/log/syslog | grep dhcpd

  * Verify that the DHCP server is listening on the correct network interface:

  sudo netstat -uap | grep dhcpd