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network interface

Debian / Ubuntu Linux Setting a Default Gateway

Q. How do I setup a default gateway on Debian or Ubuntu Linux? My router IP is 192.168.1.254 and I’d like to setup this as a default gateway for Debian Linux.

A. You can use command line tool such as
a] ip command – show / manipulate routing, devices, policy routing and tunnels

b] route command – show / manipulate the IP routing table

c] Save routing information to a configuration file so that after reboot you get same default gateway.

ip command to set a default router to 192.168.1.254

Login as the root and type:
# ip route add default via 192.168.1.254
OR
$ sudo ip route add default via 192.168.1.254

route command to set a default router to 192.168.1.254

Login as the root and type:
# route add default gw 192.168.1.254
OR
$ sudo route add default gw 192.168.1.254

Save routing information to a configuration file /etc/network/interfaces

Open /etc/network/interfaces file
# vi /etc/network/interfaces
OR
$ sudo vi /etc/network/interfaces
Find eth0 or desired network interface and add following option
gateway 192.168.1.254
Save and close the file. Restart networking:
# /etc/init.d/networking restart
OR
$ sudo /etc/init.d/networking restart

Sysadmin because even developers need heroes!!!

Linux change ip address

Q. How do I change ip address in Linux?

A. There are different ways to change IP address in Linux
(a) Command Line tools

(b) Modify configuration files

(c) Use GUI tools

Task: Display current IP address and setting for network interface called eth0

Use ifconfig command:
# ifconfig eth0
Output:

eth0      Link encap:Ethernet  HWaddr 00:30:48:5A:BF:46  
          inet addr:10.5.123.2  Bcast:10.5.123.63  Mask:255.255.255.192
          inet6 addr: fe80::230:48ff:fe5a:bf46/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:728204 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1097451 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:62774749 (59.8 MiB)  TX bytes:1584343634 (1.4 GiB)
          Interrupt:177 

Task: Change IP address

You can change ip address using ifconfig command itself. To set IP address 192.168.1.5, enter command:
# ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up
# ifconfig eth0

To make permanent changes to IP address you need to edit configuration file according to your Linux distribution.

Change IP address under RedHat / CentOS / Fedora core Linux

=> Please read – Howto change and setup IP address in Redhat Linux

Change IP address under Debian / Ubuntu Linux

=> Please read – Howto change and setup IP address in Ubuntu / Debian based Linux distros

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Iptables Open FTP Port 21 and 20

How do I open port 21 using Linux iptables firewall?
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Commonly used UNIX / Linux commands by new user

Q. . I’m a new Linux user. Can you tell me commonly used Linux / UNIX command?
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