Linux - Basico

Basics Of IP Networking
Setting up Hostname
Setting up DNS
Setting up IP address
Setting up Second IP address or Virtual IP address in Debian
Setting your default gateway
Network testing basics
Networking and IP address tools These tools are really usefull.
Ethernet Bonding Configuration in Debian
Change your network card MAC Address
Basics of IP networking
A Debian host may haveseveral interfaces each with a different Internet Protocol (IP) address. Interfaces may be of several different types, including:
Loopback: lo
Ethernet: eth0, eth1
Wi-Fi: wlan0, wlan1, wifi0,
Token Ring: tr0, tr1
PPP: ppp0, ppp1
 
There is a wide range of other network devices available, including SLIP, PLIP (serial and parallel line IP), "shaper" devices for controlling the traffic oncertain interfaces, frame relay, AX.25, X.25, ARCnet, and LocalTalk.
 
Every network interface connected directly to the Internet (or to any IP-based network) is identified by a unique 32 bit IP address. The IP address can be divided into the part that addresses the network and the part that addresses the host. If you take an IP address, set to 1 the bits that are part of the network address andset to 0 the bits that are part of the host address then you get the so-called netmask of the network.
 
Traditionally, IP networks were grouped into classes whose net address parts were 8, 16 or 24 bits in length. This system was inflexible and wasted many IP addresses, so today IPv4 networks are allocated with network address parts of varying length.
 
               IP addresses            net mask      length
     Class A   1.0.0.0     - 126.255.255.255  255.0.0.0     =  /8
     Class B   128.0.0.0  - 191.255.255.255  255.255.0.0   = /16
     Class C   192.0.0.0  - 223.255.255.255  255.255.255.0 = /24
 
IP addresses not in these ranges are used for special purposes.
There are address ranges in each class reserved for use on local area networks(LANs). These addresses are guaranteed not to conflict with any addresses on the Internet proper. (By the same token, if one of these addresses is assigned to a host then that host must not access the Internet directly but must access it through a gateway that acts as a proxy for individual services or else does Network Address Translation.) These address ranges are given in the following table alongwith the number of ranges in each class.
 
     network addresses            length  how many
     Class A   10.x.x.x                     /8      1
     Class B   172.16.x.x -  172.31.x.x     /16     16
     Class C   192.168.0.x - 192.168.255.x /24     256
 
The first address in an IP network is the address of the network itself. The last address is the broadcastaddress for the network. All other addresses may be allocated to hosts on the network. Of these, the first or the last address is usually allocated to the Internet gateway for the network.
 
The routing table contains the kernel's information on how to send IP packets to their destinations. Here is a sample routing table printout for a Debian host on a local area network (LAN) with IP address192.168.50.x/24. Host 192.168.50.1 (also on the LAN) is a router for the corporate network 172.20.x.x/16 and host 192.168.50.254 (also on the LAN) is a router for the Internet at large.
 
     # route
     Kernel IP routing table
     Destination   Gateway         Genmask       Flags Metric Ref Use Iface
     127.0.0.0     *               255.0.0.0     U     0       0     2 lo
    192.168.50.0 *              255.255.255.0 U     0      0   137 eth0
     172.20.0.0    192.168.50.1   255.255.0.0   UG    1      0     7 eth0
     default       192.168.50.254 0.0.0.0       UG    1      0    36 eth0
The first line after the heading says that traffic destined for network 127.x.x.x will be routed through lo, the loopback interface.
The second line says...