Network > DHCP Server
This chapter contains the following sections:
The SonicWALL security appliance includes a DHCP (Dynamic Host Configuration Protocol) server to distribute IP addresses, subnet masks, gateway addresses, and DNS server addresses to your network clients. The Network > DHCP Server page includes settings for configuring the SonicWALL security appliance’s DHCP server.
You can use the SonicWALL security appliance’s DHCP server or use existing DHCP servers on your network. If your network uses its own DHCP servers, make sure the Enable DHCP Server checkbox is unchecked.
The number of address ranges and IP addresses the SonicWALL DHCP server can assign depends on the model, operating system, and licenses of the SonicWALL security appliance. For example, on a SonicWALL TZ 170 SP Wireless running SonicOS Enhanced, the SonicWALL DHCP Server can assign a total of 64 address ranges with 64 IP addresses each or a total of 4,096 IP addresses.
DHCP Server Options Overview
This section provides an introduction to DHCP server options feature. This section contains the following subsections:
What Is the SonicWALL DHCP Server Options Feature?
The SonicWALL DHCP server options feature provides support for DHCP options, also known as vendor extensions, as defined primarily in RFCs 2131 and 2132. DHCP options allow users to specify additional DHCP parameters in the form of pre-defined, vendor-specific information that is stored in the options field of a DHCP message. When the DHCP message is sent to clients on the network, it provides vendor-specific configuration and service information. The “DHCP Option Numbers” provides a list of DHCP options by RFC-assigned option number.
The SonicWALL DHCP server options feature provides a simple interface for selecting DHCP options by number or name, making the DHCP configuration process quick, easy, and compliant with RFC-defined DHCP standards.
How Does the SonicWALL DHCP Server Options Feature Work?
The SonicWALL DHCP server options feature allows definition of DHCP options using a drop-down menu based on RFC-defined option numbers, allowing administrators to easily create DHCP objects and object groups, and configure DHCP generic options for dynamic and static DHCP lease scopes. Once defined, the DHCP option is included in the options field of the DHCP message, which is then passed to DHCP clients on the network, describing the network configuration and service(s) available.
The SonicWALL DHCP server options feature supports the following standards:
DHCP Server Persistence Overview
What is DHCP Server Persistence?
DHCP server persistence is the ability of the firewall save DHCP lease information and to provide the client with a predictable IP address that does not conflict with another use on the network, even after a client reboot.
DHCP server persistence provides a seamless experience when a user reboots a workstation. The DHCP lease information is saved, and the user retains the same workstation IP address. When a firewall is restarted, usually due to maintenance or an upgrade, DHCP server persistence provides the following benefits:
• IP address uniqueness: Lease information is stored in flash memory, so the risk of assigning the same IP address to multiple users is nullified
• Ease of use: By saving the lease information in the flash memory, the user’s connections are automatically restored
How Does DHCP Server Persistence Work?
DHCP server persistence works by storing DHCP lease information periodically to flash memory. This ensures that users have predicable IP addresses and minimizes the risk of IP addressing conflicts after a reboot.
Enabling the DHCP Server
If you want to use the SonicWALL security appliance’s DHCP server, select Enable DHCP Server on the Network > DHCP Server page.
Select Enable Conflict Detection to turn on automatic DHCP scope conflict detection on each zone.
DHCP Server Lease Scopes
The DHCP Server Lease Scopes table displays the currently configured DHCP IP ranges. The table shows:
• Type: Dynamic or Static
• Lease Scope: The IP address range, for example 172.16.31.2 - 172.16.31.254
• Interface: The Interface the range is assigned to--LAN, OPT, or WLAN
• Details: Detailed information about the lease, displayed as a tool tip when you hover the mouse pointer over the Details icon
• Enable: Check the box in the Enable column to enable the DHCP range. Uncheck it to disable the range
• Configure: Click the configure icon to configure the DHCP range