Software switch

Software switch

A software switch, or soft switch, is a virtual switch that is implemented at the software, or firmware level, rather than the hardware level. A software switch can be used to simplify communication between devices connected to different FortiGate interfaces. For example, using a software switch, you can place the FortiGate interface connected to an internal network on the same subnet as your wireless interfaces. Then devices on the internal network can communicate with devices on the wireless network without any additional configuration such as additional security policies, on the FortiGate unit.

It can also be useful if you require more hardware ports on for the switch on a FortiGate unit. For example, if your FortiGate unit has a 4-port switch, WAN1, WAN2 and DMZ interfaces, and you need one more port, you can create a soft switch that can include the 4-port switch and the DMZ interface all on the same subnet. These types of applications also apply to wireless interfaces and virtual wireless interfaces and physical interfaces such as those with FortiWiFi and FortiAP unit.

Similar to a hardware switch, a software switch functions like a single interface. A software switch has one IP address; all of the interfaces in the software switch are on the same subnet. Traffic between devices connected to each interface are not regulated by security policies, and traffic passing in and out of the switch are affected by the same policy.


There are a few things to consider when setting up a software switch:

  • Ensure you create a back up of the configuration.
  • Ensure you have at least one port or connection such as the console port to connect to the FortiGate unit. If you accidentally combine too many ports, you will need a way to undo any errors.
  • The ports that you include must not have any link or relation to any other aspect of the FortiGate unit. For example, DHCP servers, security policies, and so on.
  • For increased security, you can create a captive portal for the switch, allowing only specific user groups access to the resources connected to the switch.


To create a software switch – web-based manager

1. Go to System > Network > Interface and select Create New.

2. For Type, select Software Switch.

3. In the Physical Interface Members option, select the interfaces to include.

4. Configure the remaining interface settings

5. Select OK.


To create a software switch – CLI

config system switch-interface edit <switch-name>

set type switch

set member <interface_list>


config system interface edit <switch_name>

set ip <ip_address>

set allowaccess https ssh ping



Soft switch example

For this example, the wireless interface (WiFi) needs to be on the same subnet as the DMZ1 interface to facilitate wireless syncing from an iPhone and a local computer. The synching between two subnets is problematic. By putting both interfaces on the same subnet the synching will work. The software switch will accomplish this.

In this example, the soft switch includes a wireless interface. Remember to configure any wireless security before proceeding. If you leave this interface open without any password or other security, it leaves open access to not only the wireless interface but to any other interfaces and devices connected within the software switch.


Clear the interfaces and back up the configuration

First, ensure that the interfaces are not being used with any other security policy or other use on the FortiGate unit. Check the WiFi and DMZ1 ports to ensure DHCP is not enabled on the interface and there are no other dependencies with these interfaces.

Next, save the current configuration, in the event something doesn’t work, recovery can be quick.


Merge the interfaces

The plan is to merge the WiFi port and DMZ1 port. This will create a software switch with a name of “synchro” with an IP address of The steps will create the switch, add the IP and then set the administrative access for HTTPS, SSH and Ping.


To merge the interfaces – CLI

config system switch-interface edit synchro

set type switch

set member dmz1 wifi


config system interface edit synchro

set ip

set allowaccess https ssh ping



Final steps

With the switch set up, you can now add security policies, DHCP servers an any other configuration that you would normally do to configure interfaces on the FortiGate unit.

Having trouble configuring your Fortinet hardware or have some questions you need answered? Check Out The Fortinet Guru Youtube Channel! Want someone else to deal with it for you? Get some consulting from Fortinet GURU!

This entry was posted in FortiGate, FortiOS, FortiOS 5.4 Handbook and tagged , on by .

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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