Modem (PPP)

For the configuration you need a serial interface and an external PPP modem on Sophos UTM. And you also need the DSL Digital Subscriber Line access data including username and password. You will get these data from your Internet Service Provider (ISP).

To configure a Modem (PPP Point-to-Point Protocol) interface, proceed as follows:

1. On the Interfaces tab, click New Interface.

   The Add Interface dialog box opens.

2. Specify the following settings:

   Name: Enter a descriptive name for the interface.

   Type: Select Modem (PPP) from the drop-down list.

   Hardware: Select an interface from the drop-down list.

   IPv4/IPv6 default GW (optional): Select this option if you want to use the default gateway of your provider.

   Username: Enter the username, provided by your ISP.

   Password: Enter the password, provided by your ISP.

   Dial String: Enter the phone number. Example: 5551230

   Comment (optional): Add a description or other information.

3. Optionally, make the following advanced settings:

   Line speed: Set the speed in bits per seconds for the connection between Sophos UTM and the modem. Common values are 57,600 Bits/s and 115,200 Bits/s.

   Flow control: Select the method to control the data flow.

   If the data is transferred via the serial connection it might happen that the system cannot process incoming data fast enough. To ensure that no data is lost, this method of controlling the data flow becomes necessary. With the serial connection two methods are available:

   • Hardware signals
   • Software signals

   Since in a PPP connection all eight bits are used for the data transfer line and the transferred data contains the bytes of the command signs Control S and Control Q, we recommend keeping the default setting Hardware and using a serial connection cable.

   Init string: Enter the string to initialize the modem. Remember that it might become necessary to adjust the init string to the modem. In this case, the init string can be gathered from the associated modem manual. If you do not have the required documentation available, keep the default setting ATZ.

   Reset string: Enter the reset string for the modem. Keep in mind that it might be necessary to adjust the reset string to the modem. In this case you can gather it from the associated modem manual. If you do not have the required documentation available, keep the default setting ATZ.

   MTU: Enter the maximum transmission unit for the interface in bytes. You must enter a value fitting your interface type here if you want to use traffic management. A sensible value for the interface type is entered by default. Changing this setting should only be done by technically adept users. Entering wrong values here can render the interface unusable. An MTU size greater than 1500 bytes must be supported by the network operator and the network card (e.g., Gigabit interface).By default, an MTU of 1492 bytes is set for the Modem (PPP) interface type.

   Default route metric: Enter the default route metric for the interface. The metric value is used to distinguish and prioritize routes to the same destination and is valid for all interfaces.

   Asymmetric (optional): Select this option if your connection's uplink and downlink bandwidth are not identical and you want the Dashboard to reflect this. Then, two textboxes are displayed, allowing you to enter the maximum uplink bandwidth in either MB/s or KB/s. Select the appropriate unit from the drop-down list.

   Displayed max (optional): Here you can enter the maximum downlink bandwidth of your connection, if you want the Dashboard to reflect it. The bandwidth can be given in either MB/s or KB/s. Select the appropriate unit from the drop-down list.

4. Click Save.

   The system will now check the settings for validity. After a successful check the new interface will appear in the interface list. The interface is not yet enabled (toggle switch is gray).

5. Enable the interface.

   Click the toggle switch to activate the interface.

   The interface is now enabled (toggle switch is green). The interface might still be displayed as being Down. The system requires a short time to configure and load the settings. Once the Up message appears, the interface is fully operable.

To show only interfaces of a certain type, select the type of the interfaces you want to have displayed from the drop-down list. To either edit or delete an interface, click the corresponding buttons.