Install DHCP Role on Windows Server 2008
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DHCP stands for Dynamic Host Configuration Protocol, and its main purpose in life is to give your computer an IP address so it can send and receive data on the network.
In the old days of computing your computers would have to be assigned IP addresses when they were setup, and the job of keeping all these IP addresses in order usually fell to a network administrator.
I can vividly remember starting a new position at a large company and having the outgoing administrator show me the spreadsheets that had all the IP addresses for the plant, along with a notepad with changes that had not been input yet. I tell you that I implemented DHCP within 2 months, because there was no way I was dealing with that headache.
This of course was back in the days of NT 4.0, but surprisingly DHCP hasn't changed that much since back then. If you have installed DHCP before on a Windows platform, you won't see too much of a difference on Server 2008, with the exception of adding support for IPv6.
How DHCP Works
Let's talk a minute about the basic workings of how DHCP works. The DHCP server sits and waits for a client computer to turn on and need an IP. It does this through a very basic 4 step process which I will explain below.
1. Discovery -- When a computer is setup to use DHCP and is attached to the network it sends out a broadcast called DHCPDISCOVER looking for a DHCP server. Alternatively, it will request the last IP used by its DHCP client.
2. Offer -- The DHCP server will respond with a lease offer that is called DHCPOFFER and includes the lease duration, IP address, subnet mask, clients MAC address, and IP address of the DHCP server.
3. Request -- Once the client computer receives the offer and accepts it, it then sends out a broadcast called DHCPRequest that contains the IP address of the DHCP server that issued the accepted client IP. This tells other DHCP servers that their offer if any was refused, and keeps the IPs free for others.
4. Acknowledgement -- The DHCP server then sends out a DHCPACK packet to the client that includes lease duration and any other configuration information needed by the client. At this point the IP configuration process is done and the client configures its network interface.
It is important to note that the majority of these messages are broadcasts which means that your routers must be configured to pass these on if the DHCP server is not on the same subnet as the client.
There are other options to get around this limitation, but really, if your router is that old, you are better off upgrading anyway.
Windows Server 2008 DHCP Install Environment
For this demo I am going to assume we have the following already setup:
- Windows Server 2008 Installed
- Active Directory Domain Services Installed
- DNS Server Installed
- Static IP on DHCP Server
The domain for this demo is named tstdemo.com and the server we are installing DHCP on is a domain controller. I normally wouldn't recommend this, but since I am using a Virtual PC to show this demo, I am going to only have one server to use.
How to Install DHCP Role on Server 2008
Ok, now that we have discussed what DHCP is and how it does its magic, let's go ahead and install the DHCP role.
1. Open Server Manager
2. In the left pane click on Roles and in the center pane click on Add Roles
3. You might get a Before You Begin page next if it hasn't been disabled before this. It just generally warns you that if you are going to install a role on this server to make sure that it has a strong password, has the latest updates loaded, and has a static IP.
You can place a check mark next to Skip this page by default, if you don't want to see this warning again or leave it blank and click Next.
4. On the Select Server Roles page go ahead and place a check next to DHCP Server in the list, then you can click Next.
5. The next screen discusses what a DHCP Server does, which we already covered but feel free to read through it again. Once you are done go ahead and click on Next.
6. For the Select Network Connection Bindings page, the wizard will list out the network adapters you have available to bind the server to for servicing clients.
In our case we only have one adapter so it is an easy choice. Select the adapters you are working with and click Next.
7. On the Specify IPv4 DNS Server Settings screen you will fill in the name of the parent domain, and at least one preferred DNS server.
Please note that the DNS server is a Mandatory fill to continue. If you have this information setup on the server already, it will use what you have in the network and Active Directory Domain Services information to pre-fill the fields.
Either confirm or input your own information and click Next.
8. The next screen asks you to specify your WINS server. If you don't know what WINS is and your network doesn't need it, consider yourself lucky!
Some legacy applications still need it though, and while I won't get into an explanation of what it does, you should find out if you are using it before proceeding.
Either select WINS is not required for applications on this network, if you're not using it, or input the WINS Server IPs if you are. Either way click on Next when you are finished.
9. The next window will allow you to add scopes to your DHCP server. Scopes are the range of IP's that are handed out to the client computers.
I am going to choose NOT to add a scope at this time, because I will go in-depth on that subject in my next article. At this time just click on Next.
10. Now we come to a new screen for Windows DHCP servers and it asks about configuring IPv6 Stateless Mode.
I will go into this subject at a later time, so for this install I am going to leave Enable DHCPv6 stateless mode for this server selected and click on Next.
11. The next screen will ask for the IPv6 DNS Server Settings, much like the IPv4 screen I am going to use the default for Parent Domain and then type ::1 for the DNS IPv6 address which is the equivalent of localhost. Click Next when done.
12. The next step is to authorize the DHCP server in Active Directory. This is done to keep rogue DHCP servers from being put on the network to service clients.
In this window you will either choose to use the currently logged in users credentials or you can use alternate ones. You can also skip this step and authorize later.
I am going to go ahead and authorize the server, since I didn't give it any scopes I am not worried about it handing out IPs before I am ready. Make your choice and click Next.
13. The last screen provides a summary of all your selections. Review your choices and then click Install to start. Please note the information message that a server reboot might be needed.
14. The installation results screen will show the status of the install, if everything went well you should see Installation Succeeded. Click on Close.
There you have it, you have now installed the DHCP role on a Windows Server 2008 machine.
In my next article we will go in depth on configuring a scope and other options for the client on the DHCP server.
