Table of Contents

Network Interface Configuration in Linux (Ubuntu/RHEL/CentOS)


Table of Contents


RHEL/CentOS

RHEL/CentOS8, 7

It is recommended to set with the nmcli or nmtui command.

It is also possible with the ifcfg-* file.
/etc/sysconfig/network-scripts/ifcfg-*

Restart Interfaces

Restart All Interfaces
# systemctl restart NetworkManager
# nmcli networking off && nmcli networking on
Restart One Interface
# nmcli c reload                <- If you change the configuration file manually

# nmcli c down ens160 && nmcli c up ens160

関連ページ


RHEL/CentOS5, 6

/etc/sysconfig/network-scripts/ifcfg-*

Configuration

Option Explanation
DEVICE the name of the physical device
BOOTPROTO none : No boot-time protocol should be used. Static IP use 'none'.
dhcp : The DHCP protocol should be used.
bootp : The BOOTP protocol should be used.
'STATIC' is invalid parameter. if you use 'STATIC', it see 'NONE'.
ONBOOT yes : This device should be activated at boot-time.
no : This device should not be activated at boot-time.
IPADDR IP address.
NETMASK the netmask value.
USERCTL yes : Non-root users are allowed to control this device.
no : Non-root users are not allowed to control this device.
HWADDR the hardware address of the Ethernet device in the form AA:BB:CC:DD:EE:FF.
SLAVE yes : This device is controlled by the channel bonding interface specified in the MASTER directive.
no : This device is not controlled by the channel bonding interface specified in the MASTER directive.
ETHTOOL_OPTS any device-specific options supported by ethtool.
GATEWAY the IP address of the network router or gateway device (if any).


Sample Configurations

Sample : DHCP

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

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
Sample : Static IP

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

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
IPADDR=192.168.1.5
NETMASK=255.255.255.0
USERCTL=no


Reference




Ubuntu

Ubuntu 20.04, 18.04

Refarence:Network - Configuration | Ubuntu

/etc/netplan/nn_xxxxx.yaml
/etc/netplan/99_config.yaml
A later loaded file will override the settings of the previously loaded file

Static IP Sample

Example 

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: false
      dhcp6: false
      addresses: [192.168.1.50/24]
      gateway4: 192.168.1.1
      nameservers:
        addresses: [192.168.1.1, 8.8.8.8, 8.8.4.4]

$ sudo netplan apply

## If [Enter] cannot be pressed within the specified number of seconds after reflection, 
## it will return to the original setting. 
## default time out is 120 seconds.
$ sudo netplan try --timeout 10   <- 10 seconds

Example 

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      addresses:
        - 10.10.10.2/24
      gateway4: 10.10.10.1
      nameservers:
          search: [mydomain, otherdomain]
          addresses: [10.10.10.1, 1.1.1.1]


Dynamic IP Address(DHCP Client)

/etc/netplan/99_config.yaml 

network:
  version: 2
  renderer: networkd
  ethernets:
    enp3s0:
      dhcp4: true

sudo netplan apply


Ubuntu 16.04

/etc/network/interfaces

DHCP Sample

~]# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto enp0s3
iface enp0s3 inet dhcp


Static IP Sample

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto ens3
#iface ens3 inet dhcp
iface ens3 inet static
address 192.168.10.30
network 192.168.10.0
netmask 255.255.255.0
broadcast 10.0.0.255
gateway 192.168.10.1
dns-nameservers 192.168.10.10




Linux Network Configuration and Command