01-01-2013, 04:09 PM
Network Address Translation (NAT)
Network Address Translation.ppt (Size: 648.5 KB / Downloads: 32)
The IP Chains/IP tables feature also provides special routing functionality Network Address Translation (NAT).
NAT is a routing technique that alters address or other header information in a packet.
IP masquerading is a type of NAT in which packets from many computers on a LAN appear to outside world as if they came from one computer.
It also allows all of the hosts on a private network to use the Internet at the price of a single IP address.
It allows use of a private (reserved) IP network address on LAN and have Linux-based router perform some clever, real-time translation of IP addresses and ports.
Difference between NAT and IP Masquerade:
NAT is the process of modifying the network addresses contained with datagram headers while they are transmitted.
IP masquerade is one type of network address translation that allows all of the hosts on a private network to use the Internet at the price of a single IP address.
Let there is a LAN using reserved network addresses.
The network has a Linux-based masquerade router providing access to the Internet.
One of the m/c on the network wishes to establish a connection to the remote host on some port no.
It sends its datagram to the masquerade router,
Which identifies this connection request as requiring masquerade services.
It accepts the datagram and substitutes its own IP address and port number for those of the source, and transmits the datagram to the destination host keeping a note in Masquerading Table.
The destination host believes it has received a connection request from the Linux masquerade host and sends a reply datagram.
The masquerade host, upon receiving this datagram, finds the association in its masquerade table and reverses the substitution it performed on the outgoing datagram.
It then transmits the reply datagram to the originating host.