All language subtitles for 19 - Elastic IPs English

So now let's talk about Elastic IP.

So when you stop and start an EC2 instance,

it will change its public IP.

And if you need to have a fixed public IP

then you need Elastic IP.

So this is for the use cases where you need to have an IP

that's going to be constant

across your usage, obviously, to instances.

So it's an IPv4 Elastic IP that you own

as long as you don't delete it.

So it's a reservation.

And so the idea is that you attach this Elastic IP

to one EC2 instance at a time

and that EC2 instance will inherit the IPv4 from it, okay?

You can remap this IP across instances

and we'll see this in the hands-on,

and you don't pay for the Elastic IP

if it's attached to a server,

which is a good thing,

but if you just reserve the Elastic IP

without attaching it to a server,

then you're going to be billed for it.

So Elastic IP, why do we use them?

Well, the use case is that you can mask the failure

of an instance or software by rapidly remapping the address

that your instance is accessible at

to another instance in your account

that is also running the software.

And by default, you can have

up to five Elastic IPs in your account.

You can ask AWS to increase that,

but the idea is that you should avoid using Elastic IPs,

at least that's my personal opinion,

unless you really, really, really have to,

this is why you can only have five Elastic IPs

in your accounts.

So other ways, an alternative for you to pass that is

that you can use a random public IP

and instead register a DNS name to it,

maybe using Route 53,

or use a load balancer,

which will have a static host name

and the load balancer is smart enough to redirect

to your correct EC2 instance.

Now let's see Elastic IPs in action.

So I have my first instance here

and I need to make sure

that I'm going to have a security group

that's going to be open.

So I'm going to find a security group

and make sure from the rules

that SSH such is going to be open

to all, to Anywhere and click on save Rule.

Here we go, we're go to go.

So I have my first instance

but I'm going to create a second instance.

I will create my second instance.

So the name is MySecondInstance.

I will choose Amazon Linux 2 on t2.micro.

For the key pair I will choose a demo key pair.

For the network settings,

I will select the existing AWS SSH security group.

And then I'm good to go.

I'm going to launch my instance and open it.

So now we have two EC2 instances being run.

And what I'm going to do is I'm going to first set them up.

So I'm gonna go

into EC2 Instance Connect, connect to my instance.

This is EC2 instance number one.

I'm going to make sure that I remove my hello.txt,

and so I'm going to,

so there's no files in here,

now I'm going to just create a new file.

I'll do it touch hello-instance-1.txt.

So we can see

now we have a file named hello-instance-1.txt available

to us, which is enough.

So I've set up my first instance.

And then for my second instance,

I'm going to do the exact same thing.

I'm going to connect to it using EC2 Instance Connect

and I'm going

to touch a new file named hello-instance-2.txt,

excuse me, which shows that yes,

we are on instance number two, okay?

So now that my two instances are available

as we can see, they have different IPv4 addresses.

And so what I'm going to do is first attach an Elastic IP

to my first instance.

So to do so on the left hand side,

I'm gonna go into Elastic IPs

and allocate a new Elastic IP address

from Amazon's pool of IPv4 address

but you could bring your own

if you wanted to.

Let's allocate this IP.

And as we can see now,

this IPv4 right here is accessible to me.

And so what I can do is

that I can attach it to my EC2 instance, so Action.

And then I can associate this Elastic IP address

with an instance

and I'm going to attach it with my first instance.

So, good, now it is associated with my first instance.

So if we go into my instances and look at my first instance,

we can see that the public IPv4 right here is 18.198,

which is the same as my IPv4 address

that is Elastic IP.

So what I mean is that if I do an SSH command now

and then I replaced the public IP

by the one I have from the Elastic IP and connect to it

and we do ls,

as we can see, I am on my instance one

because it says hello-instance-1.txt.

So, okay, I can disconnect.

And what I will do is I will launch the exact same command

but after remapping my Elastic IPv4,

so what I can do is go back to my Elastic IP, Action.

I will disassociate this Elastic IP.

So this is going to remove it

from my current EC2 instance.

And then I will associate this Elastic IP

but this time with my second instance,

and then Associate.

So now it has been associated

with the second EC2 instance.

And so if I rerun this command right here

so we are in, okay, and we get us some warning

because the remote host identification has changed.

So I'm on the different EC2 instance.

And this is the security that my SSH command has,

which is saying that,

hey, it looks like you're connected to a different host

even though you're using the same command.

So this is expected for us,

but this is a nice warning

to know in case you're being attacked.

And so if I do clear my screen and do ls,

this time I see hello-instance-2.txt,

which shows that I am connected to my second instance.

So this is really the power of Elastic IP here.

You can use the same command and be redirected

to two different instances.

And so this is how we can mask the failure of instance one,

for example, by remaking the Elastic IP

to the second instance.

So to finish this, please make sure

to terminate your second instance

and go to your Elastic IPs.

And what you can do is just disassociate this Elastic IP.

And then when this is done

you can release the Elastic IP address

in order not to be billed for it,

because it will be unused.

Okay, so that's it for this lecture.

I hope you liked it.

And I will see you in the next lecture.