Configuring command line network inteface in Debian Rumi, May 1, 2011February 13, 2012 Configure the Network Manually You can use ip or ifconfig command to configure IP address and other information. Task: Display the Current Network Configuration Type the following command: $ ip address show Output: 1: lo: mtu 16436 qdisc noqueue link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast qlen 100 link/ether 00:19:d1:2a:ba:a8 brd ff:ff:ff:ff:ff:ff inet 192.168.2.1/24 brd 192.168.2.255 scope global eth0 inet6 fe80::219:d1ff:fe2a:baa8/64 scope link valid_lft forever preferred_lft forever 3: ra0: mtu 1500 qdisc pfifo_fast qlen 1000 link/ether 00:17:9a:0a:f6:44 brd ff:ff:ff:ff:ff:ff inet 192.168.1.106/24 brd 192.168.1.255 scope global ra0 inet6 fe80::217:9aff:fe0a:f644/64 scope link valid_lft forever preferred_lft forever 4: ppp0: mtu 1496 qdisc pfifo_fast qlen 3 link/ppp inet 10.1.3.103 peer 10.0.31.18/32 scope global ppp0 You can also use ifconfig -a command, enter: $ ifconfig -a Output: eth0 Link encap:Ethernet HWaddr 00:19:D1:2A:BA:A8 inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::219:d1ff:fe2a:baa8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15819 errors:0 dropped:0 overruns:0 frame:0 TX packets:27876 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:1695948 (1.6 MB) TX bytes:40399983 (38.5 MB) Base address:0x1000 Memory:93180000-931a0000 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:11943 errors:0 dropped:0 overruns:0 frame:0 TX packets:11943 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:7024449 (6.6 MB) TX bytes:7024449 (6.6 MB) ppp0 Link encap:Point-to-Point Protocol inet addr:10.1.3.103 P-t-P:10.0.31.18 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1496 Metric:1 RX packets:34922 errors:0 dropped:0 overruns:0 frame:0 TX packets:15764 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:3 RX bytes:50535608 (48.1 MB) TX bytes:1256881 (1.1 MB) ra0 Link encap:Ethernet HWaddr 00:17:9A:0A:F6:44 inet addr:192.168.1.106 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::217:9aff:fe0a:f644/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:73809 errors:0 dropped:0 overruns:0 frame:0 TX packets:31332 errors:1 dropped:1 overruns:0 carrier:0 collisions:27 txqueuelen:1000 RX bytes:61373519 (58.5 MB) TX bytes:5007190 (4.7 MB) Interrupt:20 The information is grouped by network interfaces. Every interface entry starts with a digit, called the interface index, with the interface name displayed after the interface index. In the above example, there are four interfaces: lo : Loopback interface, used to access local services such as proxy or webserver http://127.0.0.1/ eth0 : The first Ethernet interface connected to network switch or router ra0 : The first wireless interface ppp0 :The first point-to-point interface, used to connect via VPN or dial up service Task: Device / Interface Statistics Type the following command: $ ip -s link show interface-name $ ip -s link show eth0 $ ip -s link show ppp0 Output: 4: ppp0: mtu 1496 qdisc pfifo_fast qlen 3 link/ppp RX: bytes packets errors dropped overrun mcast 50537336 34946 0 0 0 0 TX: bytes packets errors dropped carrier collsns 1257745 15776 0 0 0 0 Change the Current Network Configuration You must login as the root to change current network settings. Task: Assign an IP Address to a Device Interface In the following example, the command assigns the IP address 192.168.1.10 to the device eth0. The network mask is 24 (255.255.255.0) bits long. The brd + option sets the broadcast address automatically as determined by the network mask. # ip address add 192.168.1.100/24 brd + dev eth0 You can also use ifconfig command, enter # ifconfig eth0 192.168.1.100 netmask 255.255.255.0 up Task: Remove / Delete / Deactivate IP address from a device interface To remove IP / delete device, enter: # ip address del 192.168.1.100 dev eth0 OR # ifconfig eth0 down Save Network Settings to a Configuration File To change the current network configuration setting you'll need to edit /etc/network/interfaces file using a text editor such as vi. This is the only way to save device setting to a configuration file so that system can remember changes after a reboot. Task: Configure a Device Statically Open /etc/network/interfaces file as the root user: # vi /etc/network/interfaces Let us assign static public routable (or private) IP address to eth0, enter: auto eth0 iface eth0 inet static address 192.168.2.1 netmask 255.255.255.0 Save and close the file. Where, auto eth0 : Identify the physical interfaces such as eth0, eth1 and so on iface eth0 inet static : This method used to define ethernet interfaces with statically allocated IPv4 addresses address 192.168.2.1 : Static IP address netmask 255.255.255.0 : Static netmask Task: Configure a Device Dynamically with DHCP Open /etc/network/interfaces file as the root user: # vi /etc/network/interfaces Let us configure eth0 using DHCP. When the device is configured by using DHCP, you don’t need to set any options for the network address configuration in the file. auto eth0 iface eth0 inet dhcp Save and close the file. Where, auto eth0 : Identify the physical interfaces such as eth0, eth1 and so on iface eth0 inet dhcp : This method used to define ethernet interfaces with DHCP server allocated IPv4 addresses Start and Stop Configured Interfaces To apply changes to a configuration file, you need to stop and restart the corresponding interface # /etc/init.d/networking stop # /etc/init.d/networking start # /etc/init.d/networking restart You can also use following command to bring down or up the eth0. Disables the device eth0, enter: # ifdown eth0 Enables eth0 again, enter: # ifup eth0 Managing DNS Entries This section explains how to configure which nameserver to use when resolving IP addresses to hostnames and vice versa. It does not explain how to configure the system as a name server. To manage DNS entries, you can add, edit, or remove DNS names from the /etc/resolv.conf file. A sample is given below: search com nameserver 204.11.126.131 nameserver 64.125.134.133 nameserver 64.125.134.132 nameserver 208.185.179.218 The search key specifies the string which will be appended to an incomplete hostname. Here, we have configured it to com. So, when we run: ping ubuntu it would be interpreted as ping ubuntu.com. Add Route route add default gw 192.168.1.129 Administrations Configurations (Linux)