Configuring additional IP addresses

Upon ordering a Dedicated Server or VPS you will receive one IPv4 address and one /64 IPv6 subnet. As an example, this could be the IPv4 address 192.51.100.10 and the IPv6 subnet 2001:0db8:2a02:c200::/64.

Your server comes pre-configured with this IPv4 (192.51.100.10) and one IPv6 address (2001:0db8:2a02:c200:0000:0000:0000:0001). Additional IPv4 addresses can be ordered by contacting us at [email protected] or through our homepage when placing an order for a new server. These additional IPv4 address will not be added to your system automatically but will have to be configured manually.

The following will give an overview on how to configure additional IP addresses on the most popular operating systems. The server used in these examples has the primary IPv4 address 192.51.100.10 and will receive the additional IPv4 addresses 192.51.100.42 and 192.0.2.23. As a general rule we recommend configuring these addresses with a netmask of 255.255.255.255 (/32) and /64 respectively and without adding a new gateway.

CentOS 6.x

CentOS has all its network interface configuration files stored in /etc/sysconfig/network-scripts/. In order to configure additional IPv4 addresses, one virtual interface per additional IPv4 address has to be created. If the main interface is e.g. eth0, the virtual interfaces would be named eth0:0, eth0:1, eth0:2 and so on. Their configurations reside in individual configuration files named ifcfg-eth0:0, ifcfg-eth0:1, ifcfg-eth0:2receptively.

#/etc/sysconfig/network-scripts/ifcfg-eth0:0 DEVICE=eth0:0 BOOTPROTO=none ONBOOT=yes IPADDR=192.51.100.42 NETMASK=255.255.255.255

#/etc/sysconfig/network-scripts/ifcfg-eth0:1 DEVICE=eth0:1 BOOTPROTO=none ONBOOT=yes IPADDR=192.0.2.23 NETMASK=255.255.255.255

Additional IPv6 addresses can be specified using the variable IPV6ADDR_SECONDARIES in the interface’s primary configuration file (/etc/sysconfig/network-scripts/ifcfg-eth0 in case of eth0). Multiple addresses are separated by a white space:

#/etc/sysconfig/network-scripts/ifcfg-eth0 ... IPV6ADDR_SECONDARIES=2001:0db8:2a02:c200:0000:0000:0000:0002/64 2001:0db8:2a02:c200:0000:0000:0000:0003/64 ...

CentOS 7.x / Fedora

The network interface configuration files of both CentOS 7.x and Fedora are stored under /etc/sysconfig/network-scripts/. Additional IPv4 addresses can be added to the respective interface’s configuration file by using variables of the pattern IPADDR0, IPADDR1, IPADDR2 and PREFIX0, PREFIX1, PREFIX2 etc., in case of e.g. eth0 this would be /etc/sysconfig/network-scripts/ifcfg-eth0:

#/etc/sysconfig/network-scripts/ifcfg-eth0 ... IPADDR0=192.51.100.42 PREFIX0=32 IPADDR1=192.0.2.23 PREFIX1=32 ...

The old method using virtual interfaces as employed in CentOS 6.x and described above will also still work.

#/etc/sysconfig/network-scripts/ifcfg-eth0 ... IPV6ADDR_SECONDARIES=2001:0db8:2a02:c200:0000:0000:0000:0002/64 2001:0db8:2a02:c200:0000:0000:0000:0003/64 ...

Debian / Ubuntu

Debian’s and Ubuntu’s network interface configuration is stored in /etc/network/interfaces. Additional IP addresses can be assigned by using the up/down commands. The following adds 192.51.100.42 and 192.0.2.23 to eth0 whose primary address is 192.51.100.10:

#/etc/network/interfaces auto eth0 allow-hotplug eth0 iface eth0 inet static address 192.51.100.10 netmask 255.255.255.255 gateway 192.51.100.1up ip addr add 192.51.100.42/32 dev eth0 down ip addr del 192.51.100.42/32 dev eth0up ip addr add 192.0.2.23/32 dev eth0 down ip addr del 192.0.2.23/32 dev eth0 ...

Additional IPv6 addresses are configured similarly:

#/etc/network/interfaces ... iface eth0 inet6 static address 2001:0db8:2a02:c200:0123:4567:89ab:0001 netmask 112 gateway fe80::1 accept_ra 0 autoconf 0 privext 0
up ip -6 addr add 2001:0db8:2a02:c200:0000:0000:0000:0002/64 dev eth0 down ip -6 addr del 2001:0db8:2a02:c200:0000:0000:0000:0002/64 dev eth0 ...

openSUSE

openSUSE has its network interface configuration files stored under /etc/sysconfig/network/. All settings concerning e.g. eth0 are saved in ifcfg-eth0, additional IPv4 and IPv6 addresses can be added using the pattern IPADDR_1, IPADDR_2, IPADDR_3 etc:

#/etc/sysconfig/network/ifcfg-eth0 ... IPADDR_1='192.51.100.42/32' IPADDR_2='192.0.2.23/32' IPADDR_3='2001:0db8:2a02:c200:0000:0000:0000:0002/64' IPADDR_4='2001:0db8:2a02:c200:0000:0000:0000:0003/64' ...