System Administration Guide: Network Services

Chapter 18 Setting Up a Leased-Line PPP Link (Tasks)

This chapter explains how to configure a PPP link that uses a leased line between peers. Major sections include the following:

Setting Up a Leased Line (Task Map)

Leased-line links are relatively easy to set up, in comparison with dial-up links. In most instances, you do not have to configure the CSU/DSU, dialing services, or authentication. If you do need to configure the CSU/DSU, refer to the manufacturer's documentation for aid with this complex task.

The task map in the next table describes all the tasks that are involved in setting up the basic leased-line link.

Note –

Some types of leased lines do require the CSU/DSU to “dial” the address of the opposite peer. For example, Frame Relay uses Switched Virtual Circuits (SVCs) or Switched 56 service.

Table 18–1 Task Map for Setting Up the Leased-Line Link



For Instructions 

1. Gather preconfiguration information 

Gather data that is needed prior to setting up the link. 

Table 16–4

2. Set up the leased-line hardware 

Assemble the CSU/DSU and synchronous interface card. 

How to Configure Synchronous Devices

3. Configure the interface card, if required 

Configure the interface script to be used when the leased line is initiated. 

How to Configure Synchronous Devices

4. Configure information about the remote peer 

Define how communications between your local machine and the remote peer should work. 

How to Configure a Machine on a Leased Line

5. Start up the leased line 

Configure your machine to start up PPP over the leased line as part of the booting process. 

How to Configure a Machine on a Leased Line

Configuring Synchronous Devices on the Leased Line

The task in this section involves configuring equipment that is required by the leased-line topology that is introduced in Example of a Configuration for a Leased-Line Link. The synchronous devices that are required to connect to the leased line include the interface and modem.

Prerequisites for Synchronous Devices Setup

Before you perform the next procedure, you must have the following items:

ProcedureHow to Configure Synchronous Devices

  1. Physically install the interface card into the local machine, if necessary.

    Follow the instructions in the manufacturer's documentation.

  2. Connect the cables from the CSU/DSU to the interface.

    If necessary, connect cables from the CSU/DSU to the leased-line jack or similar connector.

  3. Configure the CSU/DSU, as instructed in the documentation from the manufacturer or network provider.

    Note –

    The provider from whom you rented the leased line might supply and configure the CSU/DSU for your link.

  4. Configure the interface card, if necessary, as instructed in the interface documentation.

    The configuration of the interface card involves the creation of a startup script for the interface. The router at LocalCorp in the leased-line configuration that is shown in Figure 16–2 uses an HSI/P interface card.

    The following script, hsi-conf, starts the HSI/P interface.

    /opt/SUNWconn/bin/hsip_init hihp1 speed=1536000 mode=fdx loopback=no \
    nrzi=no txc=txc rxc=rxc txd=txd rxd=rxd signal=no 2>&1 > /dev/null

    Indicates that HSI/P is the synchronous port used


    Set to indicate the speed of the CSU/DSU

See Also

To configure the local machine on the leased line, refer to How to Configure a Machine on a Leased Line.

Configuring a Machine on the Leased Line

The task in this section explains how to set up a router to function as the local peer on your end of a leased line. The task uses the leased line that was introduced in Example of a Configuration for a Leased-Line Link as an example.

Prerequisites for Configuring the Local Machine on a Leased Line

Before you perform the next procedure, you must have completed the following:

ProcedureHow to Configure a Machine on a Leased Line

  1. Become superuser on the local machine (router) or assume an equivalent role.

    Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services.

  2. Add an entry for the remote peer in the router's /etc/hosts file.

    # cat /etc/hosts
    # Internet host table
    #       localhost  local2-peer        loghost  local1-net       farISP

    The example /etc/hosts file is for the local router at the fictitious LocalCorp. Note the IP address and host name for the remote peer farISP at the service provider.

  3. Create the file /etc/ppp/peers/peer-name to hold information about the provider's peer.

    For this example leased-line link, you create the file /etc/ppp/peers/farISP.

    # cat /etc/ppp/peers/farISP
    init '/etc/ppp/conf_hsi'

    The following table explains the options and parameters that are used in /etc/ppp/peers/farISP.



    init '/etc/ppp/conf_hsi'

    Starts the link. init then configures the HSI interface by using the parameters in the script /etc/ppp/conf_hsi.


    Tells the pppd daemon not to change the state of the Data Terminal Ready (DTR) signal. Also tells pppd to ignore the Data Carrier Detect (DCD) input signal.


    Gives the device name of synchronous interface. 


    Establishes synchronous encoding for the link.


    Establishes that the local system does not need to demand authentication from the peer. However, the peer could still demand authentication.

    Defines the IP addresses of the local peer and the remote peer, separated by a colon. 


    Tells the pppd daemon on the local machine to go quiet after issuing maximum number of LCP Configure-Requests and to wait for the peer to start.


    Tells the pppd daemon to try to restart the link after a connection ends.

    noccp, nopcomp, novj, noaccomp

    Disables the Compression Control Protocol (CCP), Protocol Field compression, Van Jacobson compression, and address and control field compression, respectively. These forms of compression accelerate transmissions on a dial-up link but could slow down a leased line. 

  4. Create an initialization script that is called demand, which creates the PPP link as part of the booting process.

    # cat /etc/ppp/demand
    if [ -f /var/run/ ] &&
       /usr/bin/kill -s 0 `/bin/cat /var/run/`
            /usr/bin/pppd call farISP

    The demand script contains the pppd command for establishing a leased-line link. The following table explains the content of $PPPDIR/demand.

    Code Sample 


    if [ -f /var/run/ ] && /usr/bin/kill -s 0 `/bin/cat /var/run/`

    These lines check to see if pppd is running. If pppd is running, it does not need to be started.

    /usr/bin/pppd call farISP

    This line launches pppd. pppd reads the options from /etc/ppp/options. The call farISP option on the command line causes it to read /etc/ppp/peers/farISP, also.

    The Solaris PPP 4.0 startup script /etc/rc2.d/S47pppd invokes the demand script as part of the Solaris booting process. The following lines in /etc/rc2.dS47pppd search for the presence of a file that is called $PPPDIR/demand.

        if [ -f $PPPDIR/demand ]; then
                    . $PPPDIR/demand

    If found, $PPPDIR/demand is executed. During the course of executing $PPPDIR/demand, the link is established.

    Note –

    To reach machines outside the local network, have users run telnet, ftp, rsh, or similar commands.

See Also

If you have followed all the procedures in this chapter, you have completed the configuration of the leased-line link. The following list provides references to related information.