Hey everybody welcome to the next video.
So in this video we can be talking about H.A. or high availability now high availability is the.
Is the process of making sure a resource of some kind is available at all times so whether this is a
Web site whether this is a software service for replication or whether it's for some other arbitrary
service.
It's the goal of it is to keep that availability up as high as possible to 100 percent.
This is very important for enterprise environments because a main site such as school going down imagine
Google dot com not working for two to four hours an hour 30 minutes five minutes 20 minutes so that
can have a massive effect on the rest of the world just based on how you used the resource is so that
can be scaled up or down depending on the the the application.
Now what this normally looks like is multiple servers or endpoints being able to provide the resources
and make it look like one.
This is done in a countless ways but we're just going to go over to pretty common ways.
The first thing is replication.
So replicating the data or the configuration between multiple servers allows the servers to be the same
between both.
So in case anything happens to the running server they can swap out and point the DNS entry let's say
of that host to the new server instead of the one that just failed and then the downtime is minimal.
There is downtime with this particular approach.
It's not the best approach.
However it's still being used where they run only set amount of machines.
And then if something goes down they fail over to an entirely different datacenter.
As an example.
So if a server goes down and just flip flops and points DNS to the other side let's say if you had one
in California you have another one in Las Vegas.
So you'd point to the Las Vegas one if something happened to the California one so that's in the case
of replication however the more common way enterprises do this now is with VIPs or virtual eyepiece.
Now this is a special type of IP that resolves physically the physical address the MAC address to multiple
different hosts.
Now depending on when you ask for the MAC address it will resolve to a different host.
And there's a lot of configuration such as round robin that can happen when it comes to this type of
configuration.
So I'm not going to go into details on how all of these are working.
A good example is if you want to look up high availability you can look up something called a proxy.
That's another way to do it.
Proxy servers are another common way to traffic data.
Apache traffic manager is another one.
So there's quite a few options that you could do.
However VIPs are commonly used because you can keep the client connecting to one endpoint without them
having to change who they're talking to.
Now that's also not just for clients but also internal applications.
So if you have an internal application that's talking to a particular IP address or a hostname that
resolves two of the then you can keep the software running.
And it will stay running even if something else on the same system has failed or the same network has
failed.
It won't because it's nothing's hard coded to go to a single specific internal IP it's all pointing
to a VP which will change depending on the process.
So you might have everything hooked into one data center.
However if you fail over one service such as the databases for example all your stuff doesn't break
because they're pointing at a VP which is now pointing at the Las Vegas data center which has backed
backup replica databases.
So this is kind of how high velocity works at a pretty high level.
It's important to understand this from an architecture standpoint and also from a red team standpoint
when you're attacking a web application.
You might be hitting for example if you found a local file inclusion or a codec or rogue remote code
execution and you start firing off commands.
Let's say 1 it works then it doesn't.
Then it works then it doesn't then it doesn't that it works.
You might have a mis configuration on one server in that load balanced cluster for a change.
And where you're only getting one machine that's actually vulnerable to what you're trying to do.
However it looks inconsistent.
So it's important to understand that architecture behind the scenes so you know what you're seeing when
you're actually going to an engagement.