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Hello everyone my name is vijay kumar Devireddy and i am glad to have you back on my episode 56 today we are discussing about Network Address Translation Network Address Translation or NAT is the process of changing an IP address while it transits across a router.Now, in network plus we discussed how this was used because we wanted to conserve public IP addresses because they were limited in IPv4.In security plus though we are going to gain an additional benefit when we use NAT,we can actually hide our internal networks from attackers.Now, the most commonly used type of NAT is what we call Port Address Translation or PAT.This is where we have a single public IP address assigned to a router and all of the private IP addresses that are assigned inside to our host.In your small office, home office network,this is most likely what you are using.Now, when a host wants to communicate out over the WAN,it's going to send the request to the router and the router is then going to forward the request out to the internet to the server that its trying to get to,on behalf of the host.And when it does this, it keeps track of the translation it does by using a unique random high port number for each request. This means if the attacker is getting your network from the outside,they are only going to see that single public IP address of the router and they are not going to see the fact that you have one, five ten or 100 hosts inside of your network, and they are not going to be able to exactly know how many devices there are or what kind they are.So, for the Security plus exam,in addition to knowing about NAT and PAT,you should remember that there is public and private IP scopes.Now, when you start talking about private IP ranges,you should have learnt those back in A plus and Network plus.If you didn't, I'm going to give you a quick review.Class A is anything that starts with a 10, so 10.0.0.0 all the way up through 10.255.255.255 Now in class B, we have IP address that start with 172.16.0.0 all the way up through 172.31.0.0 Essentially anything that starts with a 172.16 all the way up through 172.31 Class C is really easy to remember as well,and its probably what you are using at home its 192.168.0.0 all the way up to 192.168.255.255 So if its starts with a 192.168,it is also a private IP address.Remember, private IP addresses cannot be transmitted over the internet So instead, once they hit your external router,it's going to use either PAT or NAT to give it a public IP address and a port number to send the information out to the internet and then receive it back.