Here is the next free video in the Active Directory free training course. This video
looks at sites and subnets. In order for Active Directory to efficiently transfer data between
different locations you need a system that can be modelled according to your physical
network. The sites feature in Active Directory allows
you to divide your network up based on your network topology. Using sites you can automatically
direct your users to local resources rather than having them access the same resources
over a wide area network. Sites also allow you to configure replication
to best use the physical layout of your network. Consider this: if you had an office in New
York and another office in London networked together, it would make sense for them to
replicate off each other. If you had another office in Washington connected to the New
York office, it would make sense for the Washington office to replicate changes from New York.
It would not make sense for Washington to replicate changes from London. Any changes
from London would be replicated to New York and then passed on from New York to Washington.
Using sites in Active Directory, you can achieve this kind of result quite easily.
So what exactly is a site? According to Microsoft, a site is a group of well connected networks,
in other words, networks that are connected together via high speed networking devices.
This means a site can be more than one subnet combined together. Just like a subnet defines
part of your network, a site defines part of your network. Given this example, let’s
say you had the network 192.168.2.0 which was located in New York.
This network is the commercial network for the New York office. Due to the business suddenly
growing, the business needed more space so they rented another floor in the building.
Since this was never planned for, it was given the network IP address 192.168.20.0. Both
networks are directly connected by a high speed router. The second floor only contains
a few employees which could not fit on the original floor.
In this case it would not make sense to have the two subnets split into two sites. Using
sites you can combine both subnets together. Given this scenario both networks would share
resources with each other. Active directory treats these two subnets as the one network
location or site.
Normally sites are connected together via a wide area network but due to the design
of your network, this may not always be the case. For example, let’s say that the Washington
office had a secure network separated by a firewall to the main network to ensure that
the company secrets stay in the secure network. In this case, even though the networks are
well connected you would create a site for the secure network.
In most cases the choice of sites will come down to different physical locations separated
by a wide area network. In other cases the choice of sites comes down to firewalls separating
networks and limited traffic can travel between the networks. Other times you may decide to
create a site for networks where the speed between networks is not that great or already
highly utilized. For example, if you had two buildings close to each other that are separated
by a wireless network that is heavily used, separating the networks into two different
sites will reduce the amount of traffic travelling over the wireless network. The point to remember
is that sites allow you to model Active Directory around your physical network.
I will now change to my Domain Controller and create sites for New York, Washington
and London. To start creating some sites for my Active
Directory infrastructure, I will first open Active Directory Sites and Services from administrative
tools under the start menu. From here, I will go down to default first
site name and expand it. When you first install Active Directory this site is created so there
is somewhere to store site related items. In it you will see the 6 domain controllers
that I have already installed, 2 each in New York, Washington and London.
You are free to create your own sites and leave the default site as is; however, most
administrators will rename the default site like this. In this case I will change the
default site to New York. The next step is to create a new site for Washington and London.
To do this, I will right click sites and select new site.
I will enter the site name, in this case Washington, and below it I will select a site link. In
the next video I will cover sites links so in this video I will select the default site
link. Like the default site, a default site link is created when Active Directory is first
installed. Once the site has been created, Windows will
give you an information dialog reminding you that further configuration is required, like
assigning a subnet to that site. Once I press o.k. I will then follow the same procedure
to create a new site for London. Once the London site has been created, I need
to create a subnet for these sites. To do this, I will right click subnets and select
new subnet. From this dialog, I need to enter in the network address slash number of bits
in the subnet mask. In this case the New York office is using
192.168.2.0 with a 24 bit subnet mask. Once I have entered in this information, I can
select the site which this subnet will be associated with.
Once I press o.k. the subnet will be created. I then need to follow the same process for
the Washington and London sites. I will enter the network address and number of bits and
select to which site that subnet belongs. So far I have only created the IPv4 sites.
If you are using IPv6 on your network you can create the subnets for IPv6 following
the same process. In the case of New York I will enter in the network address followed
by the number of bits just like IPv4 and once again select the site New York for the new
subnet. Once the New York subnet is created I will
once again follow the same procedure for the Washington and London subnets. Once you have
created the subnets you will not be able to change them; however, you can always delete
a subnet and create a new one if it is not correct. You can also add or remove subnets
from a site at any time if required. If I go back to New York and look at the servers
container, notice that all my Domain Controllers are under here even though they are not located
in that site. To fix this, it is a simple matter to drag and drop each domain controller
into the correct site. When I move the first server I will get a
dialog reminding me that moving the domain controller from site to site like this may
change the settings that are applied to that server in group policy. I will cover group
policy later in the course so for the present I will ignore this message.
If these domain controllers were promoted after the sites were created, DCPromo would
detect the site and the IP address of the Domain Controller and place the Domain Controller
in the correct site. For this reason you would normally not need to move a Domain Controller
like this unless you decided to physically move the Domain Controller from one site to
another after it had been promoted. You may notice when creating sites and subnets
that the process is quite repetitive and slow. Once done you are unlikely to make changes,
or at least make changes very often. If you have worked in an IT helpdesk, you
may have come across an end user in a panic because all their important files have been
deleted. On closer inspection it is shown that the files have been accidently moved
to another location because of a misclick. To protect your sites and subnet from misclicks
you can open the properties for any of the objects, select the object tab and tick the
box protect object from accidental deletion. Once this option is ticked, if an attempt
is made to move or delete the object, a message will appear saying access is denied. In order
to move or delete the object, this tick box must be cleared. Considering how long it takes
to setup the sites and subnets and how rare it is for changes to occur, it is worth taking
the time to tick this box. That’s it for creating sites and subnets
in Active Directory. In the next video I will look at how replication and site links work
in Active Directory. Site links form the backbone for replication in Active Directory to match
the design and current state of your network. Thanks for watching another free video from
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