Heroin.
And we'll come back.
Now, in today's video, we will be discussing about the prefix lists.
Now, at a high level overview of prefix list is a set of one or more cinder blocks.
Now the overall concept of prefix list is that you can go ahead and create a prefix list from the IP
addresses that you frequently make use of and reference them as a set in a security group rules and
routes instead of referencing them individually.
For example, let's say you have a set of four cinder blocks and these four key idea blocks you're using
in multiple set of security groups across your region.
Now, instead of adding each rule manually, what you can do, you can combine all of this rule together
in a centralized structure, call as a prefix list, and then you can associate this prefix list directly
in the security group or maybe in the root table.
So this approach becomes much more easier.
Now, in the later stage, let's say that you want to update a specific kid or block Now in the first
case where you use to manually add these IP addresses in security group, let's say you have ten security
groups, and if the second city block is updated, then you will have to update all of the ten security
groups.
Now, in case of prefix list, you can just update the security group in the prefix list and there is
nothing else to change.
Things will be updated.
So this is a great approach and let's try it out.
Now, currently I'm in the VPC console within here.
Let's go ahead and open up the managed prefix list.
Now, at this stage you'll see that there are certain prefix lists that are available.
You will see you have a prefix list for Dynamo DB and three.
Now if you'll open this up, let's explore the entries.
You will see that there are certain entries available.
This is associated with the three service.
Then for the Dynamo DB.
Again for entries you have a certain set of entries that are available.
So these are basically the Amazon managed prefix list.
Now you can also create your own prefix list in case if you want to do that.
So let's go ahead and try it out so I can create my own prefix list.
Let's call it as on premise kids here, you'll have to specify the maximum entries.
This is very important.
So one important again here.
They have already mentioned that maximum entries cannot be changed after the prefix list is created.
So let's say I'll specify maximum entries at three.
Now again, it is important that if you do not have let's say you only have five C ideas, then you
do not really specify 20 maximum entries.
We'll be discussing why you should not do that, but let's keep it simple as of now.
So I'll just specify three and within the prefix entry list, let's go ahead and specify.
I'll set 1070 700 16.
Let's add one more block 1060 600 16.
All right, we'll just add two.
As of now, we'll go ahead and create a prefix list.
Perfect.
So under the entries, you have two entries.
Now, you can also see the association from here.
Now, let's go ahead and look into how we can associate this prefix list with the security group.
Let's open up one of the security groups and within one of the security groups that we have, let's
edit the inbound rules here.
Let's add a rule of Port 22.
And within here you have a prefix list where you can go ahead and specify.
So our prefix list name is on premise SSIDs.
You can go ahead and save the rule.
All right.
So if we quickly look, this is how it looks like now at the later stage, let's assume that one of
the SSID has changed off your prefix list.
You can easily modify it, let's say, from 1066 to, let's say 1040, let's save the prefix list.
So it really becomes much more easier when you go ahead and modify things at a prefix list level.
Now, in the association as well, you can also see the resources where this prefix list is associated.
In this case, it is one security group.
All right.
So I hope you understood the basics of prefix list.
Now, just to revise, there are two primary types of prefix list.
One is the customer managed prefix list, and second is the managed prefix list.
A managed prefix list is something that will not be able to modify.
However, you'll have control over your customer manage prefix list.
All right, so now comes the time of some of the important pointers that you need to note.
First one is that a prefix list supports only a single type of IP addressing only.
So you can either use IPV four or you can either use IPV six.
You cannot combine both the IPV four and the IPV six addresses in a single prefix list.
Second important point is that a prefix list applies only to the region where you have created and.
The third pointer here is very important.
It states that when you reference a prefix list in a resource, the maximum number of entries for the
prefix list counts against the quota for the number of entries for the resource.
For example, if you have a prefix list with a maximum entry of 20 and you reference that prefix list
in a security group, then this will count that you have added 20 security group rules.
This is very important.
Many might assume that this might be a hacky way because security group rules has a limitation on the
number of maximum rules that you can add, and many try to use this as a hacky method, but this does
not really work.
And this also gives us the importance of setting up the right set of maximum number of entries within
the prefix list.
If you just go ahead and randomly add a higher number.
However, the key ideas of your on premise network is lower, then ultimately it will affect the overall
limit that might be applied to a resource grid.
So with this will conclude today's video.