Technical Tip: Configuring a FortiGate with an Inbuilt DSL Modem for German Telekom DSL Connection

Prerequisites:

Before proceeding with the configuration, ensure the following conditions are met:

• Deutsche Telekom provides a modem configured in bridge mode.
• A PPPoE username and password are provided by Deutsche Telekom.
• The Deutsche Telekom modem is connected to the FortiGate DSL port.

Configuration steps:

1. Access the FortiGate CLI.
2. Configure the DSL interface by entering the following commands:

config system interface
    edit "dsl"
        set vlanforward enable
        set phy-mode vdsl2
        set tc-mode ptm
        set profiles 17a 35b       <----- Optional (commonly used by Deutsche Telekom, may not apply).

        set mtu-override enable    <----- May be required (to accommodate the 8 byte header of PPPoE).

        set mtu 1492               <----- May be required (to accommodate the 8 byte header of PPPoE).
        set annex b
    next
    edit "TELEKOM_DSL"
        set mode pppoe
        set username [USERNAME]
        set password [PASSWORD]
        set interface "dsl"
        set vlanid 7
    next
end

With this configuration, the FortiGate should establish a DSL connection with Deutsche Telekom.

Related articles:

• Troubleshooting Tip: VDSL issues on FortiGate 80F-DSL 
• Technical Tip: How to configure PPPoE connection with VLAN tag