This article explains how to create a serial Modem (PPP) interface on Sophos UTM.
This article focuses on a single interface type. To learn more about other interface types, please view KB article 118899
Known to apply to the following Sophos product(s) and version(s)
What To Do
Interfaces may be added and edited in the WebAdmin interface under: Interfaces & Routing | Interfaces | Interfaces.
- Click the 'New Interface' button to add a new interface.
- In the Type field, select: 'Modem (PPP)'
- The following image and table outline the options available, and how to fill them out:
|Interface Image ||Configuration Options |
Name: This is the name that will be shown throughout the UTM configuration, wherever this interface is referenced. Names that indicate, or are specific to, purpose, are often the most useful. For example names like: Internal, DMZ, Guest, External. or External-XO, External-ATT, are purpose-specific names that make it clear to someone who didn't create the object, what purpose it serves.
Hardware: Any detected and unused serial modems connected to the UTM are shown. If a connected modem is not detected, you may need to reboot the UTM with the modem connected and powered on, in order to see it. If the modem is not seen even after a reboot, then it may not be compatible.
IPv4 Default GW: If the interface is a connection to the internet, then a default gateway IP may be set by enabling this option. If it is not an internet connection, then this option does not normally need to be enabled.
Username: The internet provider will provide credentials to use when connecting to their service. The supplied username should be entered here.
Password: The internet provider will provide credentials to use when connecting to their service. The supplied password should be entered here.
Dial String: Enter the phone number to be dialed here.
Comment: (Optional) This is a free text field where brief comments may be recorded.
Line Speed: The default value is normally correct, although some older modems may require a slower serial port connection speed.
Flow Control: This should be left at Hardware, unless the serial device does not support it.
INIT String: If necessary, additional or alternate modem commands may be supplied for initializing the modem before dialing.
Reset String: If necessary, additional or alternate modem commands may be supplied for initializing the modem when disconnecting.
MTU: Dial-UP RAS servers typically use an MTU of 576. Setting the value to 576 may improve performance for this connection type.
Displayed max: (Optional) The displayed max value is a numeric field that is used for display purposes only. Entering the correct value in this field to match the available bandwidth provided on this link, allows the UTM to show accurate percentage graphs for each interface on dashboard. This has no impact on network behavior, as it is only used for display purposes.