How to Add a Second IP Address on Debian and OS based on Debian using Netplan

Adding a second IP address on Debian with Netplan involves editing the Netplan configuration file. Here are the steps for this process:

Check for the Existence of a Network Interface:

Ensure that you have a network interface installed, such as eth0. You can check this using the following command:

ifconfig

Look for the line corresponding to your network interface

Backup the Netplan Configuration File

It's a good practice to create a backup of the current Netplan configuration. You can do this by copying the configuration file:

sudo cp /etc/netplan/01-netcfg.yaml /etc/netplan/01-netcfg.yaml.bak

Edit the Netplan Configuration File:

Open the Netplan configuration file for editing. For example, use the nano text editor:

sudo nano /etc/netplan/01-netcfg.yaml

Add the Second IP

Add a new address block for the second IP address. For instance, if you want to add the IP address 192.168.1.3:

network:
  version: 2
  ethernets:
    eth0:
      addresses:
        - 192.168.1.2/24
        - 192.168.1.3/24
      gateway4: 192.168.1.1
      nameservers:
        addresses:
          - 8.8.8.8
          - 8.8.4.4

Ensure to specify the correct interface (eth0), IP addresses, subnet mask, gateway, and DNS settings

Apply the Netplan Configuration

Apply the changes made to the Netplan configuration:

sudo netplan apply

Check the New IP

Verify whether the second IP address has been added using the ifconfig or ip addr command:

ifconfig

or

ip addr

you should see the additional IP address associated with your network interface

Prevent cloud-init from Modifying Network Settings

To avoid interference from cloud-init, which may alter network settings, follow the instructions on this page to restrict cloud-init from making network configuration changes