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Chapter 31. Configuring ip networking with ifcfg files

This section describes how to configure a network interface manually by editing the ifcfg files.

Important

NetworkManager supports profiles stored in the keyfile format. However, by default, NetworkManager uses the ifcfg format when you use the NetworkManager API to create or update profiles.

In a future major RHEL release, the keyfile format will be default. Consider using the keyfile format if you want to manually create and manage configuration files. For details, see Manually creating NetworkManager profiles in keyfile format.

Interface configuration (ifcfg) files control the software interfaces for individual network devices. As the system boots, it uses these files to determine what interfaces to bring up and how to configure them. These files are usually named ifcfg-name, where the suffix name refers to the name of the device that the configuration file controls. By convention, the ifcfg file’s suffix is the same as the string given by the DEVICE directive in the configuration file itself.

31.1. Configuring an interface with static network settings using ifcfg files

This procedure describes how to configure a network interface using ifcfg files.

Procedure

  • To configure an interface with static network settings using ifcfg files, for an interface with the name enp1s0, create a file with the name ifcfg-enp1s0 in the /etc/sysconfig/network-scripts/ directory that contains:

    • For IPv4 configuration: 

      DEVICE=enp1s0
BOOTPROTO=none
ONBOOT=yes
PREFIX=24
IPADDR=10.0.1.27
GATEWAY=10.0.1.1

    • For IPv6 configuration: 

      DEVICE=enp1s0
BOOTPROTO=none
ONBOOT=yes
IPV6INIT=yes
IPV6ADDR=2001:db8:1::2/64

Additional resources

  • nm-settings-ifcfg-rh(5) man page

31.2. Configuring an interface with dynamic network settings using ifcfg files

This procedure describes how to configure a network interface with dynamic network settings using ifcfg files.

Procedure

  1. To configure an interface named em1 with dynamic network settings using ifcfg files, create a file with the name ifcfg-em1 in the /etc/sysconfig/network-scripts/ directory that contains: 

    DEVICE=em1
BOOTPROTO=dhcp
ONBOOT=yes

  2. To configure an interface to send:

    • A different host name to the DHCP server, add the following line to the ifcfg file: 

      DHCP_HOSTNAME=hostname

    • A different fully qualified domain name (FQDN) to the DHCP server, add the following line to the ifcfg file: 

      DHCP_FQDN=fully.qualified.domain.name
    Note

    You can use only one of these settings. If you specify both DHCP_HOSTNAME and DHCP_FQDN, only DHCP_FQDN is used.

  3. To configure an interface to use particular DNS servers, add the following lines to the ifcfg file: 

      PEERDNS=no
  DNS1=ip-address
  DNS2=ip-address

    where ip-address is the address of a DNS server. This will cause the network service to update /etc/resolv.conf with the specified DNS servers specified. Only one DNS server address is necessary, the other is optional.

31.3. Managing system-wide and private connection profiles with ifcfg files

This procedure describes how to configure ifcfg files to manage the system-wide and private connection profiles.

Procedure

The permissions correspond to the USERS directive in the ifcfg files. If the USERS directive is not present, the network profile will be available to all users.

  • As an example, modify the ifcfg file with the following row, which will make the connection available only to the users listed: 

    USERS="joe bob alice"