Linux : Basic Network Configuration , Set ip,eth0,gateway,netmask Temporarily or Permanent

For latest Redhat Linux OS versions, we can configure network in few steps.

There are two types of methods are there for network configuration

• Temporary: In which IP temporarily will be assigned to Ethernet card, and will gone across reboot or  network restart.

• Permanent: In which network configuration will be set permanently (in config files), so will be consistent across the reboot or network restart.

We will see both types here, before that we will need few things kinda prerequisite as below:

Sample Set-up Scenario : Linux Static TCP/IP Settings

IP address: 192.168.1.50

Netmask: 255.255.255.0

Hostname: UL_SERVER

Gateway IP: 192.168.1.1

Display All interfaces ( Including Disabled Interfaces )

# ifconfig -a

Dislplay only Active/Enable Ineterface

#ifconfig

Disable and Enable an Interface

# ifconfig eth0 down

# ifconfig eth0 up

Method  1 - Temporary Netwok Setup

Assign ip-address to an Interface and set netmask and broadcast for the same

# ifconfig eth0 192.168.1.50

# ifconfig eth0 netmask 255.255.255.0

# ifconfig eth0 broadcast 192.168.1.255

or in a single command

# ifconfig eth0 192.168.1.50 netmask 255.255.255.0 broadcast 192.168.1.255

Set default gateway :

route add default gw 192.168.1.1 eth0

Now we can check and verfiy this configuration like following :

#ifconfig eth0

eth0   Link encap:Ethernet  HWaddr 00:2D:32:3E:39:3B

inet addr:192.168.1.50  Bcast:192.168.1.255  Mask:255.255.255.0

inet6 addr: fe80::21d:92ff:fede:499b/64 Scope:Link

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

RX packets:977839669 errors:0 dropped:1990 overruns:0 frame:0

TX packets:1116825094 errors:8 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:2694625909 (2.5 GiB)  TX bytes:4106931617 (3.8 GiB)

Interrupt:185 Base address:0xdc00

# netstat -r         // this command will print Kernel level routing table

Kernel IP routing table

Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface

192.168.1.0      *                    255.255.255.0   U            0   0          0 eth0

default           192.168.1.1     0.0.0.0               UG          0   0          0 eth0

Note : As its a temporary setup and will be gone across the reboot or network restart

Method 2 – Permanent Network Configuration

For static IP configuration you need to edit the following files. Edit /etc/sysconfig/network as follows, enter:

# cat /etc/sysconfig/network

NETWORKING=yes

HOSTNAME=UL_SERVER

GATEWAY=192.168.1.1

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

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

DEVICE=eth0

BOOTPROTO=static

HWADDR=00:30:36:56:B1:01

IPADDR=192.168.1.50

NETMASK=255.255.255.0

ONBOOT=yes

Finally, you need to restart the networking service as below

# /etc/init.d/network restart

Note :- It will be a static permanent network configuration , so will be there across reboot and network restart.

To verify new static ip configuration for eth0

# ifconfig eth0

# route -n

#netstat -rn

That`s it , the very basic network configuration part done here.

Cheers !!

AJ