NAT Explained | Overload, Dynamic & Static

hey what's up guys welcome to servers in this video we're going to be talking about network address translation or NAT for short we're going to be looking at the problem so why NAT is needed we're going to be looking at the solution so why not helps to solve that problem and we're going to be looking at the three different types of NAT so to understand that we must first understand the problem that NAT helps to solve to do this we have to take a look back in time all the way back to the 1970s 1980s which in terms of technology seems like centuries ago way back then a group of people sat back in their chairs and they said we've done it we've created all the IP addresses we'll ever need and we shall call it IP version 4 now if you were saying that same room it'd probably agree see back then no one would ever have guessed how big Internet would grow in fact IP version 4 creates over 4 billion addresses and given that the internet was not really designed to be used by everyone this was a massive number but as the internet grew and more and more devices required addresses we quickly began to run out luckily some very clever people caught on to this early and devised a plan to help prolong the life of IP version 4 until they could come up with a new version which we know as IP version 6 so the solution they came up with can you guess what it was that's right private addresses bet you for asking to see nap then no private addresses were developed to help prolong the life of IP version 4 what these people did was create three groups of addresses and call them private addresses these addresses can be used over and over again so what we're left with is a small group of addresses that can be used billions of times trillions even over and over and over again there is one slight catch though these addresses can only be used inside an internal network they are not allowed over the public Internet I see an example let's say this is your home here is your computer here is your printer and here is your tablets they all assigned a private address from the 192.168 0/0 group this works fine communicating with each other they get along pretty happily but if these addresses can't access the public Internet does that mean they can't do anything outside of their internal network let's add a Rooter into the equation when you sign up with an isp they will give you a public address this can be used on the internet but usually they only give you one so with all these devices how can we use just one public address this is where NAT comes into play NAT converts private addresses to public addresses let's take a closer look at how this works we will simplify this to make it easier to understand first we'll look at Pat which stands for poor address translation also known as overload this is by far the most popular version of an app and is what you'll be using in your home when your computer sends data to the Rooter the reader takes a look at it looks at the source address the port number the destination address and the destination port number now the port number is very important here not only will distinguish which device the data belongs to but it also tells the device which application that data belongs to very simply the Rooter swaps out the private source address and port number then swaps it for a public address and port number the port number will often stay the same but if it's already being used then the next available one will be selected to keep track of which public addresses belong to which private addresses the Rooter builds a NAT table this table matches the private address and port number to the public address and port number once the Rooter swaps the addresses and adds it to the table it rebuilds the data and sends it on its way when the data comes back the route again looks at the addresses the source address is now the address where it came from some web service somewhere doesn't really matter the destination is now the public address important number the routed looked at this and checks the destination against the net table if it finds a match the route of will swap out the public address and port number for the private address and port number it will then send it on his way once the computer has the data the port number will tell which application to send it to if you're searching the internet for example it can even tell which tab to send data to dynamic NAT dynamic now actually goes against everything I've just said it doesn't save addresses because it's a one-to-one mapping of addresses but it's still a type of nap nonetheless the dynamic nap need to manually create a pool of public addresses this would require you to purchase these public addresses from your ISP our pool would be represented by this bucket because I didn't really know how to draw a pool apart from that dynamic NAT works in pretty much the same way when data comes in the route looks at the source and destination address swaps out the source address for the first available public address from that pool and then it sends it on its way when the data comes back it again looks at the source address then looks at the destination address if it finds a match in the NAT table from the destination address it swaps out for the private and then send us it on its way after this is done the public address will return to the pool ready to be used again lastly we take a look static net static nap requires you to manually type in the entries to the net table you tell the router which private address and port number translate to which public address and port number once this is done it works just like the other two versions when the data comes in it checks the NAT table for the source address when it finds a match is swaps the address for the public address and then sends it on its way when the data comes back rejects the address against the NAT table swaps the public for the private address and again sends it on its way this version of that is mostly used for public servers like web servers for example where the port will always be 80 for example for HTTP so that translates private addresses to public addresses it does this by using an app table to keep a record of these translations very clever but pretty simple if you enjoyed this video and we hope you did please give us a thumbs up comment and subscribe these videos are for you so if you want more let us know that's it for network address translation thank you for watching you

Channel: CertBros

Views: 180,860

Rating: 4.9467444 out of 5

Keywords: NAT explained, Network Address Translation Explained, How NAT works, How network address translation works, NAT cisco, nat, network address translation, certbros, cisco, ccent, ccna, public ip to private ip pat, private ipv4 addresses, nettwork adress transaction, static nat dynamic nat and pat

Id: qij5qpHcbBk

Length: 8min 45sec (525 seconds)

Published: Wed Nov 23 2016