USB Modem Interfaces

You configure two types of interfaces for USB modem connectivity: a physical interface and a logical interface called the dialer interface:

The USB modem physical interface uses the naming convention umd0. The Services Router creates this interface when a USB modem is connected to the USB port.
The dialer interface, dln, is a logical interface for configuring dialing properties for USB modem connections.

See the interface naming conventions in the JUNOS Software Interfaces and Routing Configuration Guide.

The following rules apply when you configure dialer interfaces for USB modem connections:

The dialer interface must be configured to use PPP encapsulation. You cannot configure Cisco High-Level Data Link Control (HDLC) or Multilink PPP (MLPPP) encapsulation on dialer interfaces.
The dialer interface cannot be configured as a constituent link in a multilink bundle.
If you are using the same dialer interface for ISDN connections and USB modem connections, the dialer interface cannot be configured simultaneously in the following modes:
- As a backup interface and a dialer filter
- As a backup interface and dialer watch interface
- As a dialer watch interface and a dialer filter
- As a backup interface for more than one primary interface