Configuring network interfaces Configure PPP and external modems
Digi TransPort® Routers User Guide
357
Configure PPP and external modems
Point-to-Point Protocol (PPP) is a standard protocol for transporting data from point to multipoint
networks (such as IP) across point-to-point links (such as a serial or ISDN connection). This
functionality is essential for dial-up Internet access.
As data is transferred across IP networks in synchronous format, the router supports asynchronous to
synchronous PPP conversion. This allows asynchronous terminals connected to the routers to
communicate with remote synchronous PPP devices. Normally, this is carried out using a single ISDN
B-channel so that data can be transferred at speeds up to 64 Kbps. This is known as ASYNC to SYNC
PPP operation and is supported as standard by most terminal adapters. To use ASYNC to SYNC PPP
operation all that is necessary is to ensure that the PPP protocol is bound to the ASY port to which the
terminal or PC is connected. (see Configuration > Network > Interfaces > Serial).
Note To use ASYNC to SYNC PPP, the attached terminal must also support PPP (Windows dial-up
networking supports PPP).
In addition to ASYNC to SYNC operation (where the router only converts the PPP from one form to
another) the router can initiate its own PPP sessions. For example, the router uses this operation
when:
n The router is configured as a router to connect an Ethernet network to the Internet via ISDN or
W-WAN.
n The router is answering an incoming ISDN call with PPP either for remote management or
remote access to the Ethernet network to which the router is connected.
n The router is accessed locally through the serial port for configuration purposes by setting up a
Windows Dial-Up-Networking connection to the phone number 123.
Note Except for MLPPP, the parameters in this section are only relevant when the router is
generating the PPP. They are not relevant for ASYNC to SYNC PPP operation.
The router also supports Multi-link PPP (MLPPP). MLPPP uses both ISDN B-channels simultaneously
(and two PPP instances), to provide data transfer speeds up to 128 Kbps for applications such as
email or establishing a point-to-point connection between two routers.
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Web
Go to Configuration > Network > Interfaces > Advanced. The Configuration > Network >
Interfaces > Advanced menu has the following sub-menu options:
n External Modems
n PPP Mappings
n PPP n
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