Linux 7 Configuring a Network Interface

External

• https://wiki.archlinux.org/index.php/Wireless_network_configuration

Internal

• Linux Network Configuration

Overview

The configuration files corresponding to the network interfaces are located in /etc/sysconfig/network-scripts.

ifcfg-eth0 example:

DEVICE=eth0
NAME=eth0
UUID=539b9873-04b8-44cc-aa01-6e9911eaa244
#HWADDR=52:54:00:70:a5:21
TYPE=Ethernet
ONBOOT=yes
BOOTPROTO=none
IPADDR=192.168.1.9
NETMASK=255.255.255.0
PREFIX=24
GATEWAY=192.168.1.1
DNS1=8.8.8.8
DEFROUTE=yes
PEERDNS=no
PEERROUTES=no
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_PEERDNS=no
IPV6_PEERROUTES=no
IPV6_PRIVACY=no
PROXY_METHOD=none
BROWSER_ONLY=no

Configuration

UUID

A unique ID for the interface.

A unique value can be created with uuidgen

HWADDR

Specifying the hardware or MAC address using the HWADDR directive will influence the device naming procedure.

DEFROUTE

Linux Routing Configuration

PEERDNS

The ifcfg parameter PEERDNS determines if the file /etc/resolv.conf is modified or not. If it is set to "yes", then the parameters DOMAIN, DNS1 and DNS2 will be used to set the search and nameserver entries in the file. If PEERDNS is set to "no", the file is not modified.

PEERDNS defaults to no unless DHCP is used, in which case it defaults to yes. If DHCP is used, usually we want to set PEERDNS to yes, unless more than one interfaces are configured, and other interface will configure DNS.

Change the IP Address

Modify/verify the following set of variables. Make sure the hardware address is correct.

DEVICE=eth0
HWADDR="08:00:27:0A:79:9F"
IPADDR="172.20.1.3"
PREFIX="16"
NETMASK="255.255.0.0"
GATEWAY="172.20.1.1"

Note that this is how a static address is changes even if NetworkManager is active.

Configure a Network Interface after Cloning a VM Image

In general, when cloning a system, you want to generated a different Mac address when cloning an image, to avoid collisions.

If "HWADDR" is set pointing to the old hardware address, we want to remove it from the cloned configuration file, because if it stays there, and the hardware address is not available, the interface won't start.

Change the UUID

Use uuidgen and replace the value from the the ifcfg-* file.