
19-1
Using Synchronous Leased Lines 19This chapter uses an example to demonstrate how to configure the PortMaster to
connect to a synchronous leased line at speeds up to T1 (1.544Mbps) or E1
(2.048Mbps). This chapter also describes how to configure a dial backup connection for
your synchronous line. The example described in this chapte r connects a PortMaster
router located in one office with a PortMaster router located in another office using a
dedicated leased line.
The following topics are described:
• “Overview of Leased Line Connections” on page 19-1
• “Configuration Steps for Leased Line Connections” on page 19-3
• “Troubleshooting a Leased Line Connection” on page 19-8
See the PortMaster Command Line Reference for more detailed command descriptions and
instructions.
Overview of Leased Line Connections
Leased line connections use leased or dedicated lines to establish a permanent
connection between two routers. Once the connection is established, it remains
available on a continuous basis whether there is network traffic between the two
locations or not. Leased line connections require a digital service unit/channel service
unit (DSU/CSU) connected between the router and the dedicated line. The DSU/CSU
takes digital data in the format used by the router and translates it into the digital
format used by the leased line. Leased line connections also require a carrier that
provides an external clock signal.
PortMaster routers support leased line connections using synchronous ports and t he PPP
protocol. In this configuration, one PortMaster is usually connected to another
PortMaster or other router over a leased line where each router uses its own Ethernet
address for the serial link—known as IP unnumbered—and the address of the other end
is discovered dynamically. In this way, a dedicated high-speed connection is established
between two routers located at separate sites. F igure19-1 shows an example of the
leased line connection.