Configure Additional Elastic IPs

For non-/32 elastic IP blocks, only the gateway IP is automatically assigned to the instance. The remaining IPs must be manually configured inside the operating system before they can be used.

Currently supported operating systems:

• Ubuntu

• CentOS

• ESXi

Before you start, make sure you have:

• The allocated EIP block (e.g., 203.0.113.16/28)

• The gateway IP (automatically assigned)

• The subnet mask (e.g., /28 → 255.255.255.240)

• The primary network interface name (e.g., wan0)

You can check the interface name using:

ip addr

Ubuntu Configuration

Applies to Ubuntu 18.04+ (Netplan-based systems)

Step 1: Edit Netplan configuration

sudo nano /etc/netplan/00-installer-config.yaml

Step 2: Add additional IPs under addresses

Example:

network:
  version: 2
  ethernets:
    eth0:
      addresses:
        - 203.0.113.17/28
        - 203.0.113.18/28
      gateway4: 203.0.113.16
      nameservers:
        addresses: [8.8.8.8,8.8.4.4]

Step 3: Apply changes

sudo netplan apply

CentOS Configuration

Applies to CentOS 7 / 8

Step 1: Edit interface configuration

sudo nano /etc/sysconfig/network-scripts/ifcfg-wan0

Step 2: Add secondary IPs

Example:

IPADDR1=203.0.113.17
PREFIX1=28

IPADDR2=203.0.113.18
PREFIX2=28

Step 3: Restart network service

sudo systemctl restart network

Or:

sudo nmcli connection reload

ESXi Configuration

Step 1: Log in to ESXi Web UI

Go to:

Networking → VMkernel NICs

Step 2: Edit the VMkernel adapter

• Add additional IPv4 addresses

• Use the same subnet mask as your elastic IP block

• Ensure gateway is correctly configured

Step 3: Save and Apply

Temporary Configuration (Linux – For Testing Only)

If you want to temporarily assign an additional elastic IP address for testing purposes without making permanent changes, use the following command:

sudo ip addr add 203.0.113.17/28 dev wan0

Note

This configuration is non-persistent and will be removed after a system reboot.

To remove the IP address manually:

sudo ip addr del 203.0.113.17/28 dev wan0

Note

• Do not modify the gateway IP assigned by the system.

• All additional elastic IPs must use the same prefix length as the allocated elastic IP block.

• Ensure security groups and firewall rules allow traffic.