When one computer contacts a name server for information

a set of records is returned.

And we're going to start talking about the different types of records right now.

The first record that we're talking about is something called the A record.

This is the most common record that you'll see returned from name servers.

And what the A record does is maps host names to IP addresses.

For example, www.example.com would be mapped to an IP address

like 1.2.3.4.

Now there's no limit on the number of A record that you can have.

You can have something like www, mail, and also a ton more.

One thing that's interesting about A records

is that you can implement them using something called an asterisk,

which stands for a wild card record.

What this would specify is that any type of query going to a certain part of that domain name

would correspond to a particular IP address.

For example, if you put *.teamtreehouse.com

then a.teamtreehouse.com, b.teamtreehouse.com,

and so on, would all point to the same IP address.

This is how a lot of multi domain web applications work.

If you've used a web application that lets you have your own custom domain

generally what they'll have is a wild card entry pointing to a specific server.

So let's go ahead and add an A record to our domain.

Now what you see here is a DNS hosting website called DNSimple,

and I am in the advanced editor for teamtreehouse.com.

Now this is not the actual DNS hosting

for teamtreehouse.com, this is just an example.

And we're going to see how to add an A record here.

So what we have here is a list of the different ns entries for teamtreehouse.com.

Now this is not what it is right now,

this is what it should be if we were actually hosting our DNS with DNSimple.

So you can disregard that.

So let's go ahead and add a record,

and I'm going to click the A record.

Now when I add an A record—

let's say I'll add Jason.teamtreehouse.com—

and you can see over on the right side of the screen here

it's going to say Jason.teamtreehouse.com resolves to,

and we don't have anything there just yet,

but when we enter the IP it would be listed right there.

Now then here we have the TTL or time to live,

and there are a few different options:

1 minute, 10 minutes, 1 hour, or 1 day.

And we can just leave it for 1 hour.

Now we'll see that that's in the list of the different records

on our teamtreehouse.com domain.

Now if we wanted to do a more complicated one

like a subdomain like hellojason—if we wanted

hello.jason.teamtreehouse.com

all we have to do is put a dot in between the words,

and as long as this is an acceptably formatted domain

it will work.

And again there is no limit on the IPs—

we're not confined to having only 1 IP per subdomain.

I'll go ahead and add that record as well.

Now if we wanted to add a wild card subdomain

we could do *.Jason.teamtreehouse—

and actually we don't need the .teamtreehouse there

now we'll do 1.2.3.4

now any single host name that we try to go to

under .Jason.teamtreehouse.com

will point to that particular IP address.

So hello.jason.teamtreehouse.com,

goodbye.jason.teamtreehouse.com—

anything that is an acceptably formatted domain

will hit that IP.

There is a very similar type of record to the A record

called a quadruple A record,

and this is the same thing as an A record

except it's for an IPv6 address.

IPv6 addresses can contain 2 more sets of information than a regular IP address,

and they're also the future of the internet.