Linux Network configuration (Ubuntu)
 		In ubuntu we can easily configure the network using graphical interface. Here we briefly look over the command line configuration.
Determining Your IP Address  
 	When Linux is installed, the ethernet device is called eth0  
 	For wireless interface it will be called wlan0  
 The ifconfig command.  
 sahab@sahab:~$ ifconfig  
 eth0      Link encap:Ethernet  HWaddr 00:1d:7d:f8:26:74   
           inet addr:192.168.2.188  Bcast:192.168.2.255  Mask:255.255.255.0 
           inet6 addr: fe80::21d:7dff:fef8:2674/64 Scope:Link 
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1 
           RX packets:173544 errors:0 dropped:0 overruns:0 frame:0 
           TX packets:98648 errors:0 dropped:0 overruns:0 carrier:0 
           collisions:0 txqueuelen:1000  
           RX bytes:197413652 (188.2 MB)  TX bytes:10905457 (10.4 MB) 
           Interrupt:20 Base address:0x8000  
  
 eth0:1    Link encap:Ethernet  HWaddr 00:1d:7d:f8:26:74   
           inet addr:192.168.1.187  Bcast:192.168.1.255  Mask:255.255.255.0 
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1 
           Interrupt:20 Base address:0x8000  
  
 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:5320 errors:0 dropped:0 overruns:0 frame:0 
           TX packets:5320 errors:0 dropped:0 overruns:0 carrier:0 
           collisions:0 txqueuelen:0  
           RX bytes:1101301 (1.0 MB)  TX bytes:1101301 (1.0 MB) 
IP Address changing
 #sudo ifconfig eth0 192.168.2.187 netmask 255.255.255.0 up
 Configuration file of netwok looks like
 # vim /etc/netwok/interfaces
 The file looks like
 auto lo                                        #For loopback address
 iface lo inet loopback 
   iface eth0 inet static                  #static ip for eth0
 address 192.168.2.188 
 netmask 255.255.255.0 
 gateway 192.168.2.254 
  iface eth0:1 inet static              #secondary ip
 address 192.168.1.187 
 netmask 255.255.255.0 
  auto eth0                                 #auto enable on boot time
 auto eth0:1
 Adding secondary ip
 #sudo ifconfig eth0:0 192.168.1.187 netmask 255.255.255.0 up
 
 Start and stop - Network  
 #sudo ifup eth0
 #sudo ifdown eth0
 #sudo /etc/init.d/networking stop
 #sudo /etc/init.d/networking start
 #sudo /etc/init.d/networking restart
 Default gateway configuration  
 sahab@sahab:~$sudo  route add default gw 192.168.2.254 eth0  
 Configuring the DNS server  
 /etc/resolve.conf  
 Vim /etc/resolve.conf
 search example.com
 nameserver 192.168.0.2
 Checking the current routing table
 sahab@sahab:~$ sudo netstat -nr  
 Kernel IP routing table 
 Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface 
 192.168.2.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0 
 192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0 
 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0 
 0.0.0.0         192.168.2.254   0.0.0.0         UG        0 0          0 eth0
Mii-tool and ethtool - Checking network card status and speed  
 sahab@sahab:~$ sudo mii-tool -v  
 eth0: negotiated 100baseTx-FD flow-control, link ok 
   product info: vendor 00:07:32, model 17 rev 2 
   basic mode:   autonegotiation enabled 
   basic status: autonegotiation complete, link ok 
   capabilities: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD 
   advertising:  100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control 
   link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control 
 
sahab@sahab:~$ sudo ethtool eth0  
 Settings for eth0: 
 	Supported ports: [ TP ] 
 	Supported link modes:   10baseT/Half 10baseT/Full  
 	                        100baseT/Half 100baseT/Full  
 	                        1000baseT/Full  
 	Supports auto-negotiation: Yes 
 	Advertised link modes:  10baseT/Half 10baseT/Full  
 	                        100baseT/Half 100baseT/Full  
 	                        1000baseT/Full  
 	Advertised auto-negotiation: Yes 
 	Speed: 100Mb/s 
 	Duplex: Full 
 	Port: Twisted Pair 
 	PHYAD: 0 
 	Transceiver: internal 
 	Auto-negotiation: on 
 	Supports Wake-on: pumbg 
 	Wake-on: g 
 	Current message level: 0x00000033 (51) 
 	Link detected: yes