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 one or more address ranges it assigns addresses from, and options such as the default gateway, DNS server, lease time, and other advanced options. 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 low-end FortiGates
On low-end FortiGate units, 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.