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Administration Guide

DHCP servers and relays

A DHCP server dynamically assigns IP addresses to hosts on the network connected to the interface. The host computers must be configured to obtain their IP addresses using DHCP. You can configure one or more DHCP servers on any FortiGate interface.

A DHCP server can be in server or relay mode. In server mode, you can define up to ten address ranges to assign addresses from, and options such as the default gateway, DNS server, lease time, and other advanced settings. In relay mode, the interface forwards DHCP requests from DHCP clients to an external DHCP server and returns the responses to the DHCP clients. The DHCP server must have appropriate routing so that its response packets to the DHCP clients arrive at the unit.

If an interface is connected to multiple networks through routers, you can add a DHCP server for each network. The IP range of each DHCP server must match the network address range. The routers must be configured for DHCP relay.

Default DHCP server for entry-level FortiGates

On entry-level FortiGates, a DHCP server is configured on the internal interface, by default, with the following values:

Field

Value

Address Range 192.168.1.110 to 192.168.1.210
Netmask 255.255.255.0
Default Gateway 192.168.1.99
Lease Time 7 days
DNS Server 1 192.168.1.99

These settings are appropriate for the default internal interface IP address of 192.168.1.99. If you change this address to a different network, you need to change the DHCP server settings to match.

A DHCP server dynamically assigns IP addresses to hosts on the network connected to the interface. The host computers must be configured to obtain their IP addresses using DHCP. You can configure one or more DHCP servers on any FortiGate interface.

A DHCP server can be in server or relay mode. In server mode, you can define up to ten address ranges to assign addresses from, and options such as the default gateway, DNS server, lease time, and other advanced settings. In relay mode, the interface forwards DHCP requests from DHCP clients to an external DHCP server and returns the responses to the DHCP clients. The DHCP server must have appropriate routing so that its response packets to the DHCP clients arrive at the unit.

If an interface is connected to multiple networks through routers, you can add a DHCP server for each network. The IP range of each DHCP server must match the network address range. The routers must be configured for DHCP relay.

Default DHCP server for entry-level FortiGates

On entry-level FortiGates, a DHCP server is configured on the internal interface, by default, with the following values:

Field

Value

Address Range 192.168.1.110 to 192.168.1.210
Netmask 255.255.255.0
Default Gateway 192.168.1.99
Lease Time 7 days
DNS Server 1 192.168.1.99

These settings are appropriate for the default internal interface IP address of 192.168.1.99. If you change this address to a different network, you need to change the DHCP server settings to match.