Example of a Configuration
for a Leased-Line Link
The tasks in Chapter 4, Setting Up a Leased-Line Point-to-Point Protocol Link show how to implement
the goal of a medium-sized organization (LocalCorp) to provide Internet
access for its employees. Currently, the employees' computers are
connected on a private corporate intranet.
LocalCorp requires speedy transactions and access to the many
resources on the Internet. The organization signs a contract with
Far ISP, a service provider, which allows LocalCorp to set up its
own leased line to Far ISP. Then, LocalCorp leases a T1 line from
Phone East, a telephone company. Phone East puts in the leased line
between LocalCorp and Far ISP. Then, Phone East provides a CSU/DSU
that is already configured to LocalCorp.
The tasks set up a leased-line link with the following characteristics.
LocalCorp has set up a system as a gateway router,
which forwards packets over the leased line to hosts on the Internet.
Far ISP also has set up a peer as a router to which
leased lines from customers are attached.
Figure 2-2 Example of a Leased-Line
In the figure, a router is set up for PPP at LocalCorp. The router connects to the corporate
Intranet through its hme0 interface. The second connection is through the
machine's HSI/P interface (hihp1) to the CSU/DSU digital unit. The CSU/DSU then connects to the
installed leased line. The administrator at LocalCorp configures the HSI/P interface and PPP files.
The administrator then types /etc/init.d/pppd to initiate the link between
LocalCorp and Far ISP.