DHCP addressing mode on an interface

DHCP addressing mode on an interface

If you configure an interface to use DHCP, the FortiGate unit automatically broadcasts a DHCP request from the interface. The interface is configured with the IP address and any DNS server addresses and default gateway address that the DHCP server provides.

DHCP IPv6 is similar to DHCP IPv4, however there is:

  • no default gateway option defined because a host learns the gateway using router advertisement messages
  • there is no WINS servers because it is obsolete.

For more information about DHCP IPv6, see RFC 3315.

Configure DHCP for an interface in System > Network > Interface and selecting the interface from the list, and selecting DHCP in the Address Mode. The table describes the DHCP status information when DHCP is configured for an interface.

Addressing mode section of New Interface page for DHCP informatio

Status                                            Displays DHCP status messages as the interface connects to the DHCP server and gets addressing information. Select Status to refresh the addressing mode status message.

Status can be one of:

  • initializing – No activity.
  • connecting – interface attempts to connect to the DHCP server.
  • connected – interface retrieves an IP address, netmask, and other set- tings from the DHCP server.
  • failed – interface was unable to retrieve an IP address and other settings from the DHCP server.


Addressing mode section of New Interface page for DHCP informatio

Obtained IP/Netmask

The IP address and netmask leased from the DHCP server. Only dis- played if Status is connected.

Renew                               Select to renew the DHCP license for this interface. Only displayed if Status is connected.


Expiry Date

The time and date when the leased IP address and netmask is no longer valid for the interface. The IP address is returned to the pool to be alloc- ated to the next user request for an IP address. Only displayed if Status is connected.


Default Gateway               The IP address of the gateway defined by the DHCP server. Only dis- played if Status is connected, and if Receive default gateway from server is selected.



Enter the administrative distance for the default gateway retrieved from

the DHCP server. The administrative distance, an integer from 1-255, spe- cifies the relative priority of a route when there are multiple routes to the same destination. A lower administrative distance indicates a more pre- ferred route.


Retrieve default gateway from server

Enable to retrieve a default gateway IP address from the DHCP server. The default gateway is added to the static routing table.


Override internal DNS

Enable to use the DNS addresses retrieved from the DHCP server instead of the DNS server IP addresses on the DNS page.

When VDOMs are enabled, you can override the internal DNS only on the management VDOM.

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