This section includes the following information:
Planning information for a leased-line link
Explanation of the sample link that is shown in Figure 16-2
For an introduction to leased-line links, refer to Leased-Line PPP Overview. For tasks about setting up the leased line, see Chapter 18, Setting Up a Leased-Line PPP Link (Tasks).
When your company rents a leased-line link from a network provider, you typically configure only the system at your end of the link. The peer at the other end of the link is maintained by another administrator. This individual might be a system administrator at a remote location in your company or a system administrator at an ISP.
Synchronous interface for your system
Synchronous unit (CSU/DSU)
Some network providers include a router, synchronous interface, and a CSU/DSU as part of the customer premises equipment (CPE). However, necessary equipment varies, based on the provider and any governmental restrictions in your locale. The network provider can give you information about the unit that is needed, if this equipment is not provided with the leased line.
Table 16-4 Planning for a Leased-Line Link
The tasks in Chapter 18, Setting Up a Leased-Line PPP Link (Tasks) 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 16-2 Example of a Leased-Line Configuration
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.
Refer to the following: