The
following section describes the process of configuring your systems IP address
and default gateway needed for communicating on a local area network and the
Internet.
Temporary IP Address
Assignment
For temporary
network configurations, you can use standard commands such as ip, ifconfig and route,
which are also found on most other GNU/Linux operating systems. These commands
allow you to configure settings which take effect immediately, however they are
not persistent and will be lost after a reboot.
To temporarily
configure an IP address, you can use the ifconfig command in the
following manner. Just modify the IP address and subnet mask to match your
network requirements.
sudo ifconfig eth0 10.0.0.100 netmask 255.255.255.0
To
verify the IP address configuration of eth0, you can use the ifconfig command
in the following manner.
ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:15:c5:4a:16:5a
inet addr:10.0.0.100 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::215:c5ff:fe4a:165a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:466475604 errors:0 dropped:0 overruns:0 frame:0
TX packets:403172654 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2574778386 (2.5 GB) TX bytes:1618367329 (1.6 GB)
Interrupt:16
To
configure a default gateway, you can use the route command in the
following manner. Modify the default gateway address to match your network
requirements.
sudo route add default gw 10.0.0.1 eth0
To
verify your default gateway configuration, you can use the route command
in the following manner.
route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0
0.0.0.0 10.0.0.1 0.0.0.0 UG 0 0 0 eth0
If
you require DNS for your temporary network configuration, you can add DNS
server IP addresses in the file /etc/resolv.conf. In general, editing /etc/resolv.conf directly
is not recommanded, but this is a temporary and non-persistent configuration.
The example below shows how to enter two DNS servers to /etc/resolv.conf,
which should be changed to servers appropriate for your network. A more lengthy
description of the proper persistent way to do DNS client configuration is in a
following section.
nameserver 8.8.8.8
nameserver 8.8.4.4
If you no longer need this configuration and wish to purge all IP
configuration from an interface, you can use the ip command with the
flush option as shown below.
ip addr flush eth0
Flushing the IP configuration using the ip command does not
clear the contents of /etc/resolv.conf. You must remove or modify those
entries manually, or re-boot which should also cause /etc/resolv.conf,
which is actually now a symlink to/run/resolvconf/resolv.conf, to be
re-written.
Dynamic IP Address Assignment
(DHCP Client)
To configure your server to use DHCP for
dynamic address assignment, add the dhcp method to the inet address
family statement for the appropriate interface in the file /etc/network/interfaces.
The example below assumes you are configuring your first Ethernet interface
identified as eth0.
auto eth0
iface eth0 inet dhcp
By adding an interface configuration as shown
above, you can manually enable the interface through the ifup command
which initiates the DHCP process via dhclient.
sudo ifup eth0
To manually disable the interface, you can
use the ifdown command, which in turn will initiate the DHCP release
process and shut down the interface.
sudo ifdown eth0
Static
IP Address Assignment
To configure your system to use a static IP
address assignment, add the static method to the inet address family
statement for the appropriate interface in the file /etc/network/interfaces.
The example below assumes you are configuring your first Ethernet interface
identified aseth0. Change the address, netmask,
and gateway values to meet the requirements of your network.
auto eth0
iface eth0 inet static
address 10.0.0.100
netmask 255.255.255.0
gateway 10.0.0.1
By adding an interface configuration as shown
above, you can manually enable the interface through the ifup command.
sudo ifup eth0
To manually disable the interface, you can
use the ifdown command.
sudo ifdown eth0
Loopback
Interface
The loopback interface is identified by the
system as lo and has a default IP address of 127.0.0.1. It can be
viewed using the ifconfig command.
ifconfig lo
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2718 errors:0 dropped:0 overruns:0 frame:0
TX packets:2718 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:183308 (183.3 KB) TX bytes:183308 (183.3 KB)
By default, there should be two lines in /etc/network/interfaces responsible
for automatically configuring your loopback interface. It is recommended that
you keep the default settings unless you have a specific purpose for changing
them. An example of the two default lines are shown below.
auto lo
iface lo inet loopback