Physical Interfaces FortiGate


FortiGate units have a number of physical ports where you connect ethernet or optical cables. Depending on the model, they can have anywhere from four to 40 physical ports. Some units have a grouping of ports labelled as internal, providing a built-in switch functionality.

In FortiOS, the port names, as labeled on the FortiGate unit, appear in the web-based manager in the Unit Operation widget, found on the Dashboard. They also appear when you are configuring the interfaces, by going to System > Network > Interface. As shown below, the FortiGate-100D (Generation 2) has 22 interfaces.

Two of the physical ports on the FortiGate-100D (Generation 2) are SFP ports. These ports share the numbers 15 and 16 with RJ-45 ports. Because of this, when SFP port 15 is used, RJ-45 port 15 cannot be used, and vice versa. These ports also share the same MAC address.



Configuring the FortiGate-100D ports

Normally the internal interface is configured as a single interface shared by all physical interface connections – a switch. The switch mode feature has two states – switch mode and interface mode. Switch mode is the default mode with only one interface and one address for the entire internal switch. Interface mode enables you to configure each of the internal switch physical interface connections separately. This enables you to assign different subnets and netmasks to each of the internal physical interface connections.

The larger FortiGate units can also include Advanced Mezzanine Cards (AMC), which can provide additional interfaces (Ethernet or optical), with throughput enhancements for more efficient handling of specialized traffic. These interfaces appear in FortiOS as port amc/sw1, amc/sw2 and so on. In the following illustration, the FortiGate-3810A has three AMC cards installed: two single-width (amc/sw1, amc/sw2) and one double-width (amc/dw).



Interface settings

In System > Network > Interface, you configure the interfaces, physical and virtual, for the FortiGate unit. There are different options for configuring interfaces when the FortiGate unit is in NAT mode or transparent mode. On FortiOS Carrier, you can also enable the Gi gatekeeper on each interface for anti-overbilling.


Interface page

Create New                                 Select to add a new interface, zone or, in transparent mode, port pair.

For more information on configuring zones, see Zones.

Depending on the model you can add a VLAN interface, a loopback inter- face, a IEEE 802.3ad aggregated interface, or a redundant interface.

When VDOMs are enabled, you can also add Inter-VDOM links.


Interface page

The names of the physical interfaces on your FortiGate unit. This includes any alias names that have been configured.

When you combine several interfaces into an aggregate or redundant inter- face, only the aggregate or redundant interface is listed, not the component interfaces.



If you have added VLAN interfaces, they also appear in the name list, below the physical or aggregated interface to which they have been added.

If you have added loopback interfaces, they also appear in the interface list, below the physical interface to which they have been added. If you have software switch interfaces configured, you will be able to view them. If your FortiGate unit supports AMC modules, the interfaces are named amc-sw1/1, amc-dw1/2, and so on.

Type                                            The configuration type for the interface.


IP/NetmasThe current IP address and netmask of the interface.

In VDOM, when VDOMs are not all in NAT or transparent mode some val- ues may not be available for display and will be displayed as “-”.

Access                                        The administrative access configuration for the interface.


Administrative Status

Indicates if the interface can be accessed for administrative purposes. If the administrative status is a green arrow, and administrator could connect to the interface using the configured access.

If the administrative status is a red arrow, the interface is administratively down and cannot be accessed for administrative purposes.


Link Status                                 The status of the interface physical connection. Link status can be either up (green arrow) or down (red arrow). If link status is up the interface is con- nected to the network and accepting traffic. If link status is down the inter- face is not connected to the network or there is a problem with the connection. You cannot change link status from the web-based manager, and typically is indicative of an ethernet cable plugged into the interface.

Link status is only displayed for physical interfaces.

MAC                                            The MAC address of the interface.

Mode                                           Shows the addressing mode of the interface. The addressing mode can be manual, DHCP, or PPPoE.

Secondary IP                             Displays the secondary IP addresses added to the interface.

Interface page

MTU                                            The maximum number of bytes per transmission unit (MTU) for the inter- face.

Virtual Domain                          The virtual domain to which the interface belongs. This column is visible when VDOM configuration is enabled.

VLAN ID                                      The configured VLAN ID for VLAN subinterfaces.


Interface configuration and settings

To configure an interface, go to System > Network > Interface and select Create New.

Name                                                  Enter a name of the interface. Physical interface names cannot be changed.


Enter an alternate name for a physical interface on the FortiGate unit. This field appears when editing an existing physical interface.

The alias can be a maximum of 25 characters. The alias name will not appears in logs.


Link Status                                        Indicates whether the interface is connected to a network (link status is Up) or not (link status is Down). This field appears when editing an existing physical interface.



Select the type of interface that you want to add.

On some models you can set Type to 802.3ad Aggregate or Redundant Interface.


Interface                                            Displayed when Type is set to VLAN.

Select the name of the physical interface to which to add a VLAN inter- face. Once created, the VLAN interface is listed below its physical inter- face in the Interface list.

You cannot change the physical interface of a VLAN interface except when adding a new VLAN interface.

Displayed when Type is set to VLAN.



Enter the VLAN ID. You cannot change the VLAN ID except when adding a new VLAN interface.

The VLAN ID can be any number between 1 and 4094 and must match the VLAN ID added by the IEEE 802.1Q-compliant router or switch con- nected to the VLAN subinterface.


Virtual Domain                                  Select the virtual domain to add the interface to.

Admin accounts with super_admin profile can change the VirtuaDomain.

This section has two different forms depending on the interface type:


Physical Interface Members

  • Software switch interface – this section is a display-only field show- ing the interfaces that belong to the software switch virtual interface.
  • 802.3ad aggregate or Redundant interface – this section includes available interface and selected interface lists to enable adding or removing interfaces from the interface.


Select interfaces from this Available Interfaces list and select the right arrow to add an interface to the Selected Interface list.


Addressing mode                            Select the addressing mode for the interface.

  • Select Manual and add an IP/Netmask for the interface. If IPv6 configuration is enabled you can add both a IPv4 and an IPv6 IP address.
  • Select DHCP to get the interface IP address and other network settings from a DHCP server.
  • Select PPPoE to get the interface IP address and other network set- tings from a PPPoE server.
  • Select One-Arm Sniffer to enable the interface as a means to detect possible traffic threats. This option is available on physical ports not configured for the primary Internet connection.
  • Select Dedicate to FortiAP/FortiSwitch to have a FortiAP unit or

FortiSwitch unit connect exclusively to the interface. This option is only available when editing a physical interface, and it has a static IP address. When you enter the IP address, the FortiGate unit auto- matically creates a DHCP server using the subnet entered. This option is not available on the ADSL interface.

The FortiSwitch option is currently only available on the FortiGate-100D.



If Addressing Mode is set to Manual, enter an IPv4 address/subnet mask for the interface. FortiGate interfaces cannot have IP addresses on the same subnet.


IPv6 Address                                    If Addressing Mode is set to Manual and IPv6 support is enabled, enter an IPv6 address/subnet mask for the interface. A single interface can have both an IPv4 and IPv6 address or just one or the other.


Administrative Access                    Select the types of administrative access permitted for IPv4 con- nections to this interface.


HTTPS                               Allow secure HTTPS connections to the web-based manager through this interface. If configured, this option will enable automatically when selecting the HTTP option.


PING                                  Interface responds to pings. Use this setting to verify your installation and for testing.


HTTP                                 Allow HTTP connections to the web-based manager through this inter- face. If configured, this option will also enable the HTTPS option.


SSH                                    Allow SSH connections to the CLI through this interface.


SNMP                                Allow a remote SNMP manager to request SNMP information by con- necting to this interface.


TELNET                             Allow Telnet connections to the CLI through this interface. Telnet con- nections are not secure and can be intercepted by a third party.


FMGAccess                     Allow FortiManager authorization automatically during the com- munication exchange between the FortiManager and FortiGate units.



You can configure a FortiGate interface as an interface that will accept FortiClient connections. When configured, the FortiGate unit sends broadcast messages which the FortiClient software running on an end user PC is listening for.


CAPWAP                           Allows the FortiGate unit’s wireless controller to manage a wireless access point, such as a FortiAP unit.


IPv6 Administrative Access

Select the types of administrative access permitted for IPv6 con- nections to this interface. These types are the same as for Admin- istrative Access.


Security Mode                                  Select a captive portal for the interface. When selected, you can define the portal message and look that the user sees when logging into the interface. You can also define one or more user groups that have access to the interface.


DHCP Server

Select to enable a DHCP server for the interface. For more information on configuring a DHCP server on the interface, see DHCP servers and relays.


Detect and Identify Devices            Select to enable the interface to be used with BYOD hardware such as iPhones. Define the device definitions by going to User & Device > Device.


Add New Devices to Vul- nerability Scan List

This option appears when Detect and Identify Devices is enabled. When enabled, the FortiGate unit performs a network vulnerability scan of any devices detected or seen on the interface. The vul- nerability scan occur as configured, either on demand, or as sched- uled.


Enforce FortiHeartBeat for all


Available when FortiHeartBeat is enabled for the Administrative Access. Select to enable sends broadcast messages which the FortiClient software running on a end user PC is listening for.

Once enabled, the FortiGate unit broadcasts a discovery message that includes the IP address of the interface and listening port number to the local network. All PCs running FortiClient on that network listen for this discovery message.


Enable Explicit Web Proxy

Available when enabling explicit proxy on the System Information Dashboard (System > Dashboard > Status).

This option is not available for a VLAN interface selection. Select to enable explicit web proxying on this interface. When enabled, this inter- face will be displayed on System > Network > Explicit Proxy under Listen on Interfaces and web traffic on this interface will be proxied according to the Web Proxy settings.


Enable STP                                       With FortiGate units with a switch interface is in switch mode, this option is enabled by default. It enables the single instance MSTP span- ning tree protocol.


Listen for RADIUS Accounting


Select to use the interface as a listening port for RADIUS content.


Secondary IP Address                     Add additional IPv4 addresses to this interface. Select the Expand

Arrow to expand or hide the section.


Comments                                         Enter a description up to 63 characters to describe the interface.


Administrative Status                      Select either Up (green arrow) or Down (red arrow) as the status of this interface.

Up indicates the interface is active and can accept network traffic.

Down indicates the interface is not active and cannot accept traffic.


Gi Gatekeeper (FortiOS Carrier only)

For FortiOS Carrier, enable Gi Gatekeeper to enable the Gi firewall as part of the anti-overbilling configuration. You must also configure Gi Gatekeeper Settings by going to System > Admin > Settings.

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About Mike

Michael Pruett, CISSP has a wide range of cyber-security and network engineering expertise. The plethora of vendors that resell hardware but have zero engineering knowledge resulting in the wrong hardware or configuration being deployed is a major pet peeve of Michael's. This site was started in an effort to spread information while providing the option of quality consulting services at a much lower price than Fortinet Professional Services. Owns PacketLlama.Com (Fortinet Hardware Sales) and Office Of The CISO, LLC (Cybersecurity consulting firm).

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