What is NAT and firewall?
Network Address Translation (NAT) refers to mechanism or device doing translation of IP addresses from one realm to another. Firewall refers to a packet filtering mechanism usually implemented at the border of a network in order to protect the internal computers from unwanted traffic or users. Many broadband home users install home routers from various vendors, such as Belkin, D-Link, LinkSys and NetGear. A home router like this serves two purposes: it works as a NAT and allows sharing of a public IP among multiple computers, and protects local computers by working as a packet-filtering firewall that blocks un-invited traffic from public Internet. Business users also use NAT and firewall features using (a) Internet routers allow them to share a few public IP addresses among many computers, and (b) Internet firewall products such as Cisco PIX, Juniper NetScreen, and CheckPoint FW1 to shield internal computers and data from outside access and rogue traffic. The above figure shows a LinkS
