So, in the last video we described how the internet works, what the internet is, is
technically an interconnected collection of networks. So, all these little networks
all over the world can now be connected to other networks in the world, and so we
have the internet which is just that. So, to understand the network here
we're bringing it down from you know the top level stuff, down to a more localized thing.
And so a local network is the type of network that you have set up in your
house, where you connect to the router, the router then you know can interact
with the internet for you, and then return the information to you computer. Now, I wanted
to talk for a moment about IP addresses and the current issues that face them, while still using
ipv4. So, let's open up a document here. So, an IP address
looks like this. This is an IP address of a server somewhere, probably, if you put
this in your browser...actually let's try. That was just a random one that I just wrote up, let's see what
happens. This is probably the address of somebody, somebody you know, somebody is
connected to an internet service provider and they get one IP address for all their
computers, and the reason why that happens is because these IP addresses can go
from 1.1.1.1 all the way to 255. So, as you can imagine the range is
pretty big but it's not quite big enough for the human population, and so we've
been running out of IP addresses for the last fifteen or twenty years. And,
multiple solutions have been brought into the equation to try and solve this
problem.
One of them was called a NAT. What this is is a network address. Basically, you have
one router you have one IP address. So, the IP address you have let's say is
this one up here at the top, this is your IP address that the internet service
provider has given you. Without the use of a router you can plug one device into the
modem and your computer will use this IP address in requests, so basically when you send a
request to google.com to load a page or to load a search what happens is your
IP address gets sent to Google as well so that Google can return this data to your
device. But, what happens when you only have one IP address and seven computers, that's
when the NAT comes into play. So, this IP address now is the IP address of your
modem or router, and it assigns NAT addresses to all the devices
on your network. So, let's say you just have two devices on the network.
The first one, actually the IP address of your actual router is likely this. I've
seen one instance where a network did not use this IP address as its routers
IP address. The IP addresses that your router will assign to computers in your home all
begin with 192. So, basically it would be something like that, right, that would be
the IP address, actually hold up I got this wrong. This is the IP address of
your router, this is the IP address of your first computer. So, it always begins with 192.168
Your second computer might be this, and your 3rd computer might be this. So, now
you have three IP addresses, three devices on your network and your router here is
keeping track of them. So, from this device I type google.com into the address bar,
what happens is this IP address along with the request gets sent to my router,
the router then sends the request off to the ISP and then over to the internet and stuff,
with the IP address of the router which internally is this and externally this is
our ISP IP address they gave us. So, what happens this gets sent to google.com, google.com sends the page
back to this IP address connected to the router here, the router then takes that
request and connects it with the device that requested it, and then it sends it
back to that device. And so that's how a router interfaces between a local
network and the internet. So, in the olden days before the NAT address and routers
really took off each one of these computers
would have had a different IP address, so it would have looked something like this.
So, that would have been 3 actual IP addresses when we found a way that you actually only need one IP
address for our network, and so that's what a router does and so these IP addresses
are local and you're gonna see these in terminal. Now, one other special IP
address is 127.0.0.1 On every computer this means this computer. It's
basically a self identifying IP address. If I were to type this into my browser I
would see my localhost, where if you put this in your browser you would see
your localhost. The NAT IP address basically works the same way. So, if I were
to go to 192.168.0.3 it would try to find a computer only on my network
that has this address and then connect to it. So, that's how a router works, in the next video we're getting
into the ifconfig. On Windows you have an ipconfig command, on Linux here you've
got ifconfig and we're gonna cover that in the next video, and a a few other commands as well. So, thank you
guys so much for watching, and I'll see you guys soon.