Linux 7 Configuring a Network Interface

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External

Internal

Overview

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

ifcfg-eth0 example: 

DEVICE="eth0"
NAME="eth0"
TYPE="Ethernet"
ONBOOT="yes"
IPADDR="192.168.1.9"
NETMASK="255.255.255.0"
PREFIX="24"
GATEWAY="192.168.1.1"
DNS1="192.168.1.1"
BOOTPROTO="none"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"
IPV6_PRIVACY="no"

Configuration

IPADDR

NETMASK

PREFIX

UUID

An 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.

DEVICE

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.

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