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Linux Static IP Configuration

Updated by Linode

Computer networks, including Linode’s, frequently use DHCP to provide IP addresses, routing and DNS information to systems which join the network. DHCP can only assign one IP address per DHCP lease request.

Additional IP addresses can be assigned using either Network Helper to automatically create a static network, or manual configuration by following this guide. Be aware that errors in network configurations may disconnect SSH sessions, so it is advised that you use the Linode Shell (LISH) when making such changes.

General Network Configuration

You’ll first need some information from the Linode Manager. Log in and go to the Remote Access tab. There you’ll find your Linode’s IPv4 and IPv6 addresses (both public and private, if you assigned a private IP), default gateways, netmasks and DNS resolvers.

Linode Manager / Remote Access

Keep this information handy, because you’ll need it as you configure your Linode’s network settings. Bear in mind that each Linode has only one virtual ethernet interface, eth0. Most outbound connections will still originate from the IP assigned to eth0, but if you need server daemons to bind to a particular IP address, you’ll need to specify the correct IP in their configuration files.

Hostname and FQDN Settings

If you haven’t already done so, set your system’s hostname and fully qualified domain name (FQDN) using our Getting Started guide.

DNS Resolver Settings

If you’ve migrated your Linode to a new datacenter, you may need to edit your resolv.conf file so that your Linode can resolve DNS queries. Your DNS nameservers are listed under the Remote Access tab of the Linode Manager (see the screenshot above).

/etc/resolv.conf
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domain members.linode.com
nameserver 203.0.113.9
nameserver 203.0.113.10
options rotate
  • domain: Sets the system’s short hostname. The search domain also defaults to this domain as well since one is not explicity specified in the file.
  • nameserver: The IPv4 or IPv6 address of a DNS resolver from the Linode Manager you wish your system to use. You can specify as many nameservers as you like and use resolvers other than Linode’s if you choose.
  • options rotate: The rotate option spreads DNS queries among the listed nameservers instead of always using the first available. This is useful in case any one DNS resolver experiences an outage.

For more info on resolv.conf, see its manual page.

Static IP Configuration

Addressing

The different IP blocks available to your Linode are:

  • Public IPv4 - /24
  • Private IPv4 - /17
  • IPv6 - /64

Some Linux distributions determine their netmask based on the assigned IP address block.

Gateways

Although your Linode may have multiple IP addresses assigned using virtual interfaces, you should only specify a default gateway for one interface. The gateway should be on the same network as the desired IP address. For example, if you have the interface eth0:3 assigned to the address 198.51.100.5, you should use 198.51.100.1 as the gateway.

A default gateway should not be specified for private IP addresses. Additionally, the subnet mask for private IPs should be set to 255.255.128.0, not 255.255.255.0.

Using the examples below, be sure the IP addresses you enter reflect those shown under the Remote Access tab of the Linode Manager.

Arch

There are multiple ways to configure static IP addresses in Arch. See the Static IP Address section of Arch’s Network Configuration Wiki page.

CentOS 7 / Fedora 22+

Edit the interface’s config file:

/etc/sysconfig/network-scripts/ifcfg-eth0
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. . .

GATEWAY=198.51.100.1

# Your primary public IP address.
# The netmask is taken from the PREFIX (where 24 is Public IP, 17 is Private IP).
IPADDR0=198.51.100.5
PREFIX0="24"

# To add a second public IP address:
IPADDR1=198.51.100.10
PREFIX1="24"

# To add a private IP address:
IPADDR2=192.0.2.6
PREFIX2="17"

CentOS 6

CentOS 6 needs interface aliases specified in its config files. This means that additional IPs are assigned to an alias you create for eth0 (for example, eth0:1, etho0:2, etc.). CentOS 6 keeps each interface configuration in a separate file at /etc/sysconfig/network-scripts/ifcfg-<interface_alias_name> so you’ll need to create one for eth0, and one for each alias you would like.

/etc/sysconfig/network-scripts/ifcfg-eth0
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# eth0
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
    
# Your primary public IP address.
IPADDR=198.51.100.5
NETMASK=255.255.255.0
GATEWAY=198.51.100.1
/etc/sysconfig/network-scripts/ifcfg-eth0:1
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# eth0:1
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes

# To add a second public IP address:
IPADDR=198.51.100.10
NETMASK=255.255.255.0

Debian / Ubuntu

Edit the interface’s config file:

/etc/network/interfaces
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. . .

# Your primary public IP address.
iface eth0 inet static
    address 198.51.100.5/24
    gateway 198.51.100.1

# To add a second public IP address:
iface eth0 inet static
    address 198.51.100.10/24

# To add a private IP address:
iface eth0 inet static
    address 192.0.2.6/17

Gentoo

Networking in Gentoo utilizes the netifrc utility. Addresses are specified in the config_eth0 line and separated by spaces.

/etc/conf.d/net
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config_eth0="198.51.100.5/24 198.51.100.10/24 192.0.2.6/17"
routes_eth0="default gw 198.51.100.1"
. . .

OpenSUSE

  1. Edit the interface’s config file:

    /etc/sysconfig/network/ifcfg-eth0
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    . . .

# Your primary public IP address.
IPADDR='198.51.100.5'
NETMASK='255.255.255.0'
GATEWAY="198.51.100.1"

# Add a second public IP address:
IPADDR1='198.51.100.10'
NETMASK1='255.255.255.0'
LABEL1='1'

# Add a private IP address:
IPADDR2='192.0.2.6'
NETMASK2='255.255.128.0'
LABEL2='2'

  2. You will also need to add your gateway to the network routes file:

    /etc/sysconfig/network/routes
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    # Destination   Gateway                 Netmask                 Device
default         198.51.100.1            255.255.255.0           eth0

Disable Network Helper

When assigning static IP addresses, Network Helper (not to be confused with NetworkManager) should be disabled to avoid it overwriting your interfaces file in the future.

  1. From the Linode Manager’s Dashboard, choose Edit for the desired configuration profile.

    Linode Manager: Dashboard > Configuration Profile > Edit

  2. Scroll to the Filesystem/Boot Helpers section at the bottom of the page. The radio button for Auto-configure Networking should be set to Yes to indicate Network Helper is enabled. To disable it, select No and click Save Changes.

    Linode Manager: Dashboard > Configuration Profile > Edit

Reboot your Linode

It’s best to reboot your Linode from the Dashboard of the Linode Manager rather than use ifconfig or an init system to restart the interfaces or distro’s network services. This ensures that the new settings take effect without issues and that the networking services reliably start in full from the boot-up.

Test Connectivity

  1. Log back into your Linode through SSH.

  2. Confirm that your /etc/resolv.conf exists and is correct.

  3. Ping each default gateway listed on the Remote Access tab of the Linode Manager:

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    ping 198.51.100.1

This guide is published under a CC BY-ND 3.0 license.