How to configure multiple DHCP scopes on one Windows server

Administrators frequently turn to the Dynamic Host Configuration Protocol (DHCP) service to streamline IP address configurations for clients. While DHCP is a cornerstone of network management, deploying a separate DHCP server for each subnet or IP address range can be impractical. This lightweight service manages essential network settings for clients, including IP addresses, subnet masks, default gateways, and DNS servers. Given its efficiency, it is more cost-effective for administrators to manage multiple DHCP scopes on a single server, thus conserving both financial resources and administrative effort. Windows Server stands out as a robust platform for DHCP, particularly when multiple scopes are deployed on a single server.

DHCP summary

Before diving into deployment, it’s crucial to grasp the fundamentals of the DHCP service. DHCP server administrators set up a scope—a designated range of IP addresses and associated settings. Clients acquire their IP configurations through a four-step lease generation process:

DHCP discover. The client broadcasts a request for a DHCP server.
DHCP offer. The DHCP server responds with an IP address configuration offer.
DHCP request. The client formally requests the offered IP address configuration.
DHCP acknowledge. The DHCP server finalizes the process by acknowledging the client’s request.

Upon completion, the client device receives a comprehensive IP address configuration.

Figure 1: Windows client displays its IP address configuration, including the DHCP Enabled, Lease Obtained, and Lease Expires information.

Deploying DHCP

Your network likely already features at least one DHCP server. If it does not, you can install the service using the following PowerShell cmdlet:

Install-WindowsFeature DHCP -IncludeManagementTools

Access the DHCP management console via the Tools menu in the Server Manager Utility. It is advisable to conduct this installation on an isolated test network to prevent experimental scopes from disrupting the existing IP address infrastructure. Prior to leasing IP addresses to clients, you must authorize the DHCP server in Active Directory. To do this, right-click the server node in the DHCP console and select the Authorize option. Domain admin or enterprise admin privileges are required for this step.

Figure 2: Verify the authorization of a DHCP server in Active Directory using PowerShell.

Deploy one DHCP server with multiple scopes

This guide illustrates a scenario where a single DHCP server is connected to multiple subnets, each requiring distinct DHCP scopes with specific router and DNS settings. An example design might include:

DevNet: 192.168.1.15-254/24, default gateway 192.168.1.1, DNS 192.168.2.10
ProdNet: 192.168.2.15-254/24, default gateway 192.168.2.1, DNS 192.168.2.10
SalesNet: 192.168.3.15-254/24, default gateway 192.168.3.1, DNS 192.168.2.10
EngineersNet: 192.168.4.15-254/24, default gateway 192.168.4.1, DNS 192.168.2.10

This design features four distinct IP address pools, each tailored with specific network service settings. The address range settings allow for addresses 15 through 254 to remain available, reserving addresses 1 through 14 for static IP assignments for devices such as printers, servers, and routers.

While one might consider deploying four separate DHCP servers—one for each subnet—this approach complicates centralized administration and may lead to inefficient use of server resources. Monitoring DHCP logs and managing configurations across multiple servers can be cumbersome. Consequently, utilizing a single DHCP server with multiple scopes is a more prudent strategy.

Create the first scope

To initiate, log in to the DHCP server, open Server Manager, and select DHCP from the Tools menu. To create DHCP scopes, expand the server icon in the DHCP console, right-click the IPv4 node, and select New Scope. Following the earlier example, create a scope named “DevNet” with the IP address range 192.168.1.50-254/24, a default gateway of 192.168.1.1, and a DNS IP address of 192.168.2.10.

Figure 3: Define an IP address range, leaving room for any static addresses you want to remain outside the scope.

The server is now equipped to lease IP addresses from this pool to client devices. While additional scope options are available, the primary configurations will focus on the default gateway and DNS server addresses.

Figure 4: Set various scope-specific options, including the DNS server IP addresses.

To manage which network interface card (NIC) the scope responds to, navigate to the DHCP console and follow these steps:

Right-click the server node.
Select Properties.
Navigate to the Advanced tab.
Select Bindings.
Check the boxes for each NIC you want the server to listen on. This setting applies server-wide, not just to individual scopes.

Once the configuration is complete, activate the scope.

Create additional scopes

To manage additional scopes effectively, install and configure a separate NIC in the DHCP server for each scope it will host. Continuing with the previous example, add three NICs to the server, assigning static IP addresses that align with the configurations of the scopes you intend to create:

eth1: 192.168.1.9/24 (associated with the DevNet scope).
eth2: 192.168.2.9/24 (ProdNet).
eth3: 192.168.3.9/24 (SalesNet).
eth4: 192.168.4.9/24 (EngineersNet).

Next, repeat the process to create the three new scopes, ensuring that you accurately input the appropriate values for the ProdNet, SalesNet, and EngineersNet configurations. Errors in DHCP scope configuration can lead to significant network challenges.

The server is now capable of hosting four unique IP address pools, which can be activated or deactivated individually.

Figure 5: Four fully configured scopes.

The primary distinction among the pools lies in their scope options, with each scope featuring unique values for the range of available addresses and the default gateway IP address.

Additionally, a server options node exists within the DHCP console under both the IPv4 and IPv6 nodes. This node allows for the configuration of global options that apply across all DHCP scopes, simplifying administration. For instance, setting the DNS server IP address option at the server level ensures it applies universally to all scopes.

Figure 6: Server options apply to all scopes, while scope options only apply to the scope on which they are set.

In cases where server and scope options conflict, the more specific scope options take precedence, granting administrators enhanced control on a per-scope basis. The DHCP console facilitates the configuration of various settings applicable to all IP addresses leased by the server (server options) while allowing for custom options that pertain to specific scopes (scope options). Furthermore, reserved IP addresses can be configured within each scope, centralizing the DHCP service within a single Windows deployment.

Damon Garn owns Cogspinner Coaction and provides freelance IT writing and editing services. He has authored multiple CompTIA study guides, including those for Linux+, Cloud Essentials+, and Server+, and contributes extensively to Informa TechTarget, The New Stack, and CompTIA Blogs.

Winsage