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Hostname and IP address lookup. What

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exactly that means is, if you have the

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hostname and you want to find the IP

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address, how does it work? We do have

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DNS, right. And there are protocols that

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we run like ping, or we go to a

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browser, and we type in the hostname or

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the website name. And it resolves to an

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IP itself, because those are the type of

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protocols that knows that it needs to

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resolve IP address first. If you don't

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have those protocols, and you just

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wanted to know the IP or hostname, then

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you will just run the commands like nslookup,

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and dig, they're two major

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commands or tools that are given to us

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in Linux. I believe they are also

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available in Windows. I'm sure nslookup

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is, but I'm not sure dig is available.

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But you could also dig for dig to find

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out if dig is available Windows. So what

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exactly these tools, or these commands

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do for us. Again, they resolve hostname

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to IP, IP to IP, or hostname to hostname.

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Let's look at them by logging into our

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system. I'm logged in to the console.

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And the command I will run is nslookup.

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When you run this, it will bring me to

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its own menu. And if I type here

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www.google.com, it is giving me the IP

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address of Google. What is right here?

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Right here is our resolver. Meaning this

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is our DNS server, our DNS server since

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we are running our machine local to our

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modem, so our modem is our DNS server.

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And our modem is also accepting requests

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for DNS and DNS port runs on port 53.

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And when you see the message here,

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Non-authoritative answer, it means that when

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I type nslookup for that IP, I, the my

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modem does not have the information for

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that google.com. It went outside on the

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internet to find that information for

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me. That is why you see that here Non-authoritative.

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If I had the information

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for Google saved in my local computer or

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in my local DNS server, then I would not

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have seen Non-authoritative answer, I

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would have gotten the straight name and

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IP address. So you could quit out of it,

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or ctrl c out of it. Clear the screen.

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So you could also run nslookup simply

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followed by www. let's say this time,

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we'll do hotmail.com. And you will see

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the Hotmail IP address is right here

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204.79.197.212. If you type this IP

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address into the Linux machine or in

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your Windows machine, you will get the

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host, you will get the page associated

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with this IP address. Similarly, the

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same command works for dig www.hotmail.com.

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And you will get the same answer but a

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little differently. So some people use

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nslookup, and some people use dig.

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Nowadays, a lot of people users are more

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inclined toward dig command as compared

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to nslookup. nslookup is a very old

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utility. and you could get a lot more

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information out of dig command as

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compared to nslookup. So try nslookup,

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or dig command on different websites

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like www.facebook.com, and then try to

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see if you could get this IP and resolve

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it to the page that you go going to. So

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any example we could try to open

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up our server right here. Oh sorry, our

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browser, and in this browser, let's close

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some of the tabs. In this browser, I will type

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[No audio]

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the IP address that shows up for

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Facebook, which is 31.13.71.36.

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You hit enter. You see it took us to

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the Facebook, took us to the

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Facebook page. That's how the Internet

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DNS works. It does not know the name, it

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only knows the IP addresses. But since

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we are humans, we tend to remember the

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names instead of IP or digits. That's

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why it's become easier for us to do is

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to use DNS that actually translates

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hostname to IP address. So try these two

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commands a few times, do run man command

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on them, and see how it works. Good luck.

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