Add and Remove IPv4 Addresses

Adding an IPv4 Address

To add an IPv4 address,

Use the following command to get the details of the existing public IPv4 address(es) of the instance:

# ip -4 -d addr show

E.g: The IP address for your instance ( CentOS-7 distribution) is 97.64.98.26 with the prefix 24. You will receive an output similar to this:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000

        inet 97.64.98.26/24 brd 206.246.84.255 scope global dynamic eth0

           valid_lft 85681sec preferred_lft 85681sec

Add the new IP address via the following command "ip addr add <ip address/prefix> dev <interface name>".
```
# ip addr add 97.64.98.36/24 dev eth0
```
You should be able to PING or login to the instance via SSH using this new IPv4.
Make this change persistent as per the distribution, refer to the distribution changes:

CentOS-7

Open and edit the file "/etc/sysconfig/network-scripts/ifcfg-eth0":
```
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
```

Add the below contents:

            BOOTPROTO=static 

            GATEWAY=97.64.98.1  

            IPADDR0=97.64.98.26 

            PREFIX0=24  

            IPADDR1=97.64.98.36 

            PREFIX1=24

Comments:
The GATEWAY address is available in the instance networking section
IPADDR0 is the main IPv4 of the instance
IPADDR1 is the newly added IPv4 to the instance
Do not make any changes to IPv6 address related entries

CentOS Stream 8, CentOS Stream 9, Fedora, Rocky Linux and Alma Linux

Make the Primary IP assigned to your instance as static.
Note: Below commands need to be executed only once, subsequent configurations to assign IPv4 addresses can be done directly.

            #  nmcli con mod "System eth0"  ipv4.addresses 97.64.98.26/24

            #  nmcli con mod "System eth0" ipv4.gateway 97.64.98.1

            #  nmcli con mod "System eth0" ipv4.method manual

            #  nmcli con mod "System eth0" connection.autoconnect yes

Comments:
The GATEWAY address is available in the instance networking section

Add the additional IPv4 address.

        # nmcli con modify "System eth0" +ipv4.addresses 97.64.98.36/24

Restart the instance.

OpenSUSE

Open and edit the file "/etc/sysconfig/network/ifcfg-eth0" by adding the default and new IPv4 address entries.

            # vi /etc/sysconfig/network/ifcfg-eth0

                # Created by cloud-init on instance boot automatically, do not edit.

                #

                BOOTPROTO=dhcp

                DHCLIENT6_MODE=info

                LLADDR=fa:16:3e:65:8b:5a

                MTU=1500

                STARTMODE=auto

             IPADDR_0=97.64.98.26/24   

              IPADDR_1=97.64.98.36/24

Note - Here, you should add the default/main IPv4 address as IPADDR_0 along with the new IPv4 address as IPADDR_1.

Ubuntu

Follow the steps below for the given distributions:

Ubuntu22.04 LTS, 20.04 LTS, 18.04 LTS, 16.04 LTS

Make a copy of the "/etc/netplan/50-cloud-init.yaml" file as "multiple-ips-init.yaml".

            # cp /etc/netplan/50-cloud-init.yaml /etc/netplan/multiple-ips-init.yaml

Open the file " /etc/netplan/multiple-ips-init.yaml" and add the address entries as below:

# vi /etc/netplan/multiple-ips-init.yaml

            network:

                version: 2

                ethernets:

                  ens3:
 
                     dhcp4: false

                     dhcp6: true

                     match:

                         macaddress: fa:16:3e:d9:58:50

                      mtu: 1500

                     set-name: ens3

                     addresses: [97.64.98.26/24,97.64.98.36/24]

                     gateway4: 97.64.98.1

Note - Here, you should add the default/main IPv4 address along with the new IPv4 address, set dhcp4 to false and provide the gateway address.

Apply the net plan to have multiple IP addresses.
```
# netplan apply
```

Debian & Ubuntu 16.04

Follow the steps below for the given distributions:

Debian11,10,9

Ubuntu16.04 LTS

Make a copy of the file "/etc/network/interfaces.d/50-cloud-init.cfg" as "multiple-ips-init.cfg".

        # cp /etc/network/interfaces.d/50-cloud-init.cfg \  

        /etc/network/interfaces.d/multiple-ips-init.cfg

Open the file "/etc/network/interfaces.d/multiple-ips-init.cfg" and add the address entries as below:

# vi /etc/network/interfaces.d/multiple-ips-init.cfg

            auto lo

            iface lo inet loopback

                      dns-nameservers 8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844


                auto ens3

                iface ens3 inet static 

                  mtu 1500

                  address 97.64.98.26/24 

                  gateway  97.64.98.1


                auto ens3:1

                allow-hotplug ens3:1

                iface ens3:1 inet static

                  address 97.64.98.36/24

Removing an IPv4 Address

To remove an IPv4 address,

Use the following command to get the details of the existing public IPv4 address(es) of the instance:

# ip -4 -d addr show

E.g: The IP address for your instance ( CentOS 7 distribution) is 97.64.98.26 with a prefix 24. You have an additional IP address associated with the instance that is 97.64.98.36 with a prefix 24. You will receive an output similar to this:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000


        inet 97.64.98.26/24 brd 206.246.84.255 scope global dynamic eth0

           valid_lft 85681sec preferred_lft 85681sec

           inet 97.64.98.36/24 brd 206.246.84.255 scope global dynamic eth0

           valid_lft 85681sec preferred_lft 85681sec

Remove the IP address via the following command "ip addr del <ip address/prefix> dev <interface name>".
```
# ip addr del 97.64.98.36/24 dev eth0
```
You should not be able to PING or login to the instance via SSH using this IPv4.
Make this change persistent as per the distribution, refer to the distribution changes:

CentOS-7

Open and edit the file "/etc/sysconfig/network-scripts/ifcfg-eth0" file.

            # vi /etc/sysconfig/network-scripts/ifcfg-eth0

Remove the entries from the file for the IPv4:

            BOOTPROTO=static

            GATEWAY=97.64.98.1

            IPADDR0=97.64.98.26

            PREFIX0=24 

            IPADDR1=97.64.98.36 

            PREFIX1=24

CentOS Stream 8, CentOS Stream 9, Fedora, Rocky Linux and Alma Linux

Remove the additional IPv4 address configured on the instance.

            # nmcli con modify "System eth0" -ipv4.addresses 97.64.98.36/24

Reboot the instance to apply the configuration.
```
            # shutdown -r now
        
```

OpenSUSE

Open and edit the file "/etc/sysconfig/network/ifcfg-eth0" to remove the entries for IPv4 address.

            # vi /etc/sysconfig/network/ifcfg-eth0

            # Created by cloud-init on instance boot automatically, do not edit.

            #

            BOOTPROTO=dhcp

            DHCLIENT6_MODE=info

            LLADDR=fa:16:3e:65:8b:5a

            MTU=1500

            STARTMODE=auto

            IPADDR_0=97.64.98.26/24 

             IPADDR_1=97.64.98.36/24

Ubuntu

Follow the steps below for the given distributions:

Ubuntu22.04 LTS, 20.04 LTS, 18.04 LTS, 16.04 LTS

If you have more than two IPv4 addresses assigned to your instance, you can un-assign a specific address by removing it from the
"/etc/netplan/multiple-ips-init.yaml" file as below:
E.g:

            network:

          version: 2

          ethernets:

            ens3:

              dhcp4: false

              dhcp6: true

              match:

                macaddress: fa:16:3e:d9:58:50

                          mtu: 1500

                          set-name: ens3

                          addresses: [97.64.98.26/24,97.64.98.36/24,97.64.98.46/24]

                          gateway4: 97.64.98.1

Or if you have only one additional IPV4 address, remove the file
"/etc/netplan/multiple-ips-init.yaml".

            # rm /etc/netplan/multiple-ips-init.yaml

Apply the net plan to remove the additional IP address.
```
 # netplan apply
```

Debian & Ubuntu 16.04

Follow the steps below for the given distributions:

Debian11,10,9

Ubuntu16.04 LTS

If you have more than two IPv4 addresses assigned to your instance, you can un-assign a specific address by removing it from the "/etc/network/interfaces.d/multiple-ips-init.cfg" file.
E.g:

            auto lo

            iface lo inet loopback

              dns-nameservers 8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844


            auto ens3

            iface ens3 inet static

               mtu 1500

               Address 97.64.98.26/24

              gateway 97.64.98.1


            auto ens3:1

            allow-hotplug ens3:1

            iface ens3:1 inet static

              address 97.64.98.36/24


           auto ens3:2 

           allow-hotplug ens3:2

           iface ens3:2 inet static

              address 97.64.98.46/24

Or, if you have less than two additional IPv4 addresses, remove the file
"/etc/network/interfaces.d/multiple-ips-init.cfg".

            # rm /etc/network/interfaces.d/multiple-ips-init.cfg

Reboot the system to remove the additional IP address permanently.
```
# shutdown -r now
```