hello and this is sunny welcome back today my topic is network address translation or net for the first two decades of the Internet the computers on a private network connected to the Internet worked this way get a block of a unique public IP addresses and assign them to each computer and the LAN side of the default gateway they assign IP address of ISPs router on the one side of the default gateway then tell each computer on the private network the default gateways IP address all IP addresses here in this setup are public IP addresses this
classic setup has at least two big problems one security vulnerability since IP addresses are public everyone can access is a so-called private network two IP address exhaustion as the internet grows larger and faster than anyone ever could imagine IP addresses were running out very quickly to solve these problems private IP addressing and a network address translation or net come to rescue proud IP addresses are afraid to anyone but not routable net is a process of a technology where a router or similar network device translates one IP address into another specifically our routers translates an internal
host a private IP address into the rotors public IP address for outgoing traffic and it also translates the runners public IP address into internal private IP address for incoming traffic net improves security because internal houses IP addresses are hidden net together with ipv4 private addressing scheme conserves ipv4 address space and thus extends is a life span there are four types of net static net dynamic net Pat and port forwarding please let me explain for you one by one [Music] Net stands for static network address translation a type of net whereas one private IP address is
mapped with one public IP address this public IP addresses never change and that's why it is called static net sunette allows an internal host such as web server to have a private IP address and still be reachable over the Internet this type of setup is useful for providing services for both internal and external users but a very wasteful of expensive public IP addresses that deals more with incoming traffic in contrast aesthetic net dynamic net deals more with outbound traffic the mapping of an internal private IP address into the routers public IP address is not static
but dynamic take a look at this example we can see whenever an internal host connects to the Internet the router would replace the internal private IP address with the first available public IP address from is a pool our public IP addresses when the packet comes back from the Internet the routers reviews the net table and the forwards the packet to the corresponding internal host dynamic net is also called IP masquerading because is Musk's the internal hosts and make is very difficult for external hackers to monitor a specific host the downsides of a dynamic net is
of course very expensive as the router would maintain a block or group of public IP addresses port address translation or pet is the most common form of network address translation with a pet each host on a line is translated to the routers one side public IP address with a different port number assignment port numbers are used to map traffic from specific hosts on a network when an internal host initiates a session with an external server his private IP address is swapped for the routers public IP address on each packet and attached with some unique port
number making each session unique returning traffic is a swapped back through the routers NAT table and ascended to the original host the mapping our internal IP address and the port number to translated IP address and port number enables perfect tracking over patties in and out Pat can handle many internal hosts with a single public IP address since tcp/ip port number space is a 16 digit value some of those port numbers are used for common protocols but tens of thousands are available for Pat to work his magic last but not least port forwarding port forwarding deals
more with incoming traffic and then the typical scenario is when you have only one public IP address but with a several public service take a look at this example we have a three servers web FTP and mail servers both for public Internet users and internal users the external users can access web server by the date with public IP address on port 80 the same principle applies to the FTP server and a mail server any inbound traffic on TCP port 21 will be forwarded to the FTP server and all inbound traffic on TCP port 25 will
be forward to the internal mail server in summary net is a technology where a public IP address a router is a swapped with a private IP address our internal host net improves security because internal hosts IP addresses are hidden net together with a private ipv4 addressing scheme comes service ipv4 addresses and it extends is lifespan otherwise a long before the year 2011 everyone would have already used IP version 6 which is another topic in another video thank you very much and see you next time all don't forget to subscribe [Music]
