You can use any number of DHCP servers on a single physical network if you divide the range of addresses that you want assigned into multiple scopes. Each scope contains a number of useful pieces of data, but before you can understand them, you need to know some additional terminology.
You can perform the following management tasks on DHCP scopes:
■ Create a scope
■ Configure scope properties
■ Configure reservations and exclusions
■ Set scope options
■ Activate and deactivate scopes
■ Create a superscope
■ Create a multicast scope
■ Integrate Dynamic DNS and DHCP
I will cover each task in the following sections.
Creating a New Scope in IPv4
Like many other things in Windows Server 2022, a wizard drives the process of creating a new scope. You will most likely create a scope while installing DHCP, but you may need to create more than one. The overall process is simple, as long as you know beforehand what the wizard is going to ask. If you think about what defines a scope, you’ll be well prepared. You need to know the following:
■ The IP address range for the scope you want to create.
■ Which IP addresses, if any, you want to exclude from the address pool.
■ Which IP addresses, if any, you want to reserve.
■ Values for the DHCP options you want to set, if any. This item isn’t strictly necessary for creating a scope. However, to create a useful scope, you’ll need to have some options to specify for the clients.
To create a scope, under the server name, right- click the IPv4 option in the DHCP snap in, and use the Action ➢ New Scope command. This starts the New Scope Wizard (see Figure 6.5). You will look at each page of the wizard in the following sections.
FIGURE 6.5 Welcome page of the New Scope Wizard
Setting the Screen Name
The Scope Name page allows you to enter a name and description for your scope. These will be displayed by the DHCP snap- in.
It’s a good idea to pick sensible names for your scopes so that other administrators will be able to figure out the purpose of the scope. For example, the name DHCP is likely not very helpful, whereas a name like 1st Floor Subnet is more descriptive and can help in troubleshooting.
Defining the IP Address Range
The IP Address Range page (see Figure 6.6) is where you enter the start and end IP addresses for your range. The wizard does minimal checking on the addresses you enter, and it automatically calculates the appropriate subnet mask for the range. You can modify the subnet mask if you know what you’re doing.
FIGURE 6.6 IP Address Range page of the New Scope Wizard
Adding Exclusions and Delay
The Add Exclusions And Delay page (see Figure 6.7) allows you to create exclusion ranges. Exclusions are TCP/IP numbers that are in the pool, but they do not get issued to clients. To exclude one address, put it in the Start IP Address field. To exclude a range, also fill in the End IP Address field. The delay setting is a time duration by which the server will delay the transmission of a DHCPOFFER message.
Although you can always add exclusions later, it’s best to include them when you create the scope so that no excluded addresses are ever passed out to clients.
FIGURE 6.7 Add Exclusions And Delay page of the New Scope Wizard
Setting a Lease Duration
The Lease Duration page (see Figure 6.8) allows you to set how long a device gets to use an assigned IP address before it has to renew its lease. The default lease duration is 8 days. You may find that a shorter or longer duration makes sense for your network. If your network is highly dynamic, with lots of arrivals, departures, and moving computers, set a shorter lease duration; if it’s less active, make it longer.
FIGURE 6.8 Lease Duration page of the New Scope Wizard
Remember that renewal attempts begin when approximately half of the lease period is over (give or take a random interval) or when a system restarts, so don’t set them too short. For example, leases that are set too short can cause renewal traffic in the middle of the workday and this can cause network delays while all the machines try to renew their addresses.
Configuring Basic DHCP Options
The Configure DHCP Options page (see Figure 6.9) allows you to choose whether you want to set up basic DHCP options such as default gateway and DNS settings. The options are described in the following sections. If you choose not to configure options, you can always do so later. However, you should not activate the scope until you’ve configured the options you want assigned.
FIGURE 6.9 Configure DHCP Options page of the New Scope Wizard
Leave a Reply