Implementing and Understanding DHCP
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The next window is where you enter any exclusions to the range of IP addresses you entered in the previous step. These exclusions are IP addresses that you do not want the DHCP server to hand out in the range specified. This is where planning ahead for static IP assignments (as mentioned earlier) comes in handy. For example, if the sales department's router has an IP address of 192.168.0.1, you'll want to make sure to exclude this from the DHCP scope (Figure 4).
Figure 4. Adding exclusions is crucial to preventing IP conflicts in DHCP networks
The next screen you will come upon is the Lease Duration dialog. Here you configure the amount of time for a standard DHCP lease (Figure 5). If you did your planning properly, you should already have an idea of what you want this to be. If you are not running any services that have an effect on DHCP leases, and you don't have a large makeup of mobile clients, then it is usually a good idea to just accept the default value.
Figure 5. Setting the IP lease duration
After you have configured lease duration, you will be prompted to configure any additional network settings. If you wish, this is where you can choose to enter default gateway, DNS server, and WINS server addresses to be distributed to network clients. Once you have completed these additional steps, you will come to the end of the New Scope Wizard, where you are prompted to activate the scope. Doing this will cause the DHCP server to begin answering DHCP discovery requests.
Configuring Additional DHCP Settings
Once you have completed setup of your first DHCP scope, you can then make changes to DHCP server and scope options from the DHCP MMC snap-in, accessible through the servers' administrative tools. There are a couple of tasks that you will commonly do from this snap-in that we will cover here.
The first of these is adding exclusions. Although we did this in our initial setup, there are often occasions where new devices are installed that require a static IP address. Whenever this happens, you will want to make sure you create an exclusion for the device. To do this, find the scope the exclusion falls under in the left pane of the DHCP snap-in and expand it. Right-click "Address Pool" and select "Add Exclusion Range." From here, type in the address or address range and click "Add" (Figure 6).
Figure 6. Adding exclusions from the DHCP MMC snap-in
The second thing that you may find yourself doing often from the DHCP snap-in is creating IP reservations. For whatever reason, you may want a client workstation to receive its address from the DHCP server, but keep the same address regardless. DHCP allows for this by tying the devices MAC (layer 2) address to an IP address in order to create a reservation of an IP address by that device. To create a reservation, you must once again expand the scope the reservation will reside under in the left pane of the MMC snap-in. After doing this, right click "Reservations," and click "New Reservation." On this screen (Figure 7), you must enter a name for the reservation, the MAC address of the network interface card on the client, the IP address you want to reserve for it, a description for the reservation, and whether or not the reservation supports DHCP and BOOTP. It is a best practice to come up with a standardized naming scheme for your IP reservations that is simple and descriptive.
Figure 7. Creating an IP reservation
It doesn't take a genius to realize how much work it would require to manually assign and manage IP addresses for even a small-sized network. That being the case, DHCP is the best logical option for automated address deployment. The Windows Server 2003 implementation of DHCP server is just the ticket and provides a solution that is both easy to configure and to manage.
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