Configuration Overview

A pppd process on a local system negotiates with the pppd process on a remote or peer system to establish the PPP connection. The following files are used for PPP connections:

/etc/ppp/Autostart starts pppd for on-demand outbound calls.
/etc/ppp/Systems contains the hostname or IP address of peers and how to connect with peers.
/etc/ppp/Devices associates dialer types with physical devices and speeds. pppd examines the file when it places a call. If no suitable speed is found or if all devices associated with that speed are busy, pppd tries again later.
/etc/ppp/Dialers describes how to dial each type of modem attached to the HP-UX system that is to be made available for outbound calls.
/etc/passwd is used to verify the login of an inbound connection.
/etc/ppp/Login is a shell script that is run after a successful login. Login starts pppd on the local system to communicate with pppd on the peer to negotiate and establish a PPP connection.

The following section describes how these files are used to create a PPP connection.

How PPP Connections are Established

In the following example, the local system "robin" attempts to connect to the peer system "lark" via PPP, as shown in Figure 2-1 “PPP Connection Example”.

Figure 2-1 PPP Connection Example

After PPP connections are configured on both systems and robin is re-booted, the Autostart file on robin starts pppd for an on-demand connection from robin to lark. If IP traffic is initiated to lark, the following occurs, as shown in Figure 2-2 “PPP Connection Example (continued)”:

Figure 2-2 PPP Connection Example (continued)

pppd searches the Systems file on robin for an entry in the name field that matches lark's hostname or IP address.
When a match of lark's hostname or IP address is found in the Systems file, the speed field in the matching entry is noted. The Devices file is then searched for an entry that matches the speed field in the Systems file entry.
When a match of the speed is found in the Devices file, the dialer field in the matching entry is noted. The Dialers file is then searched for an entry that matches the dialer field in the Devices file entry.
The phone number for lark is dialed.
The chat script specified for "lark" in the Systems file sends robin's login name and password to lark.
lark verifies robin's password by comparing it to the entry in its /etc/passwd file.
If the login is successful, the Login shell script specified in the /etc/passwd entry is executed. The Login script starts pppd on lark to communicate with pppd on robin. The two pppd's negotiate and establish a PPP connection.

Configuration Quick Reference

The following table shows the steps in configuring oubound and inbound PPP connections. Each step is described in more detail in the sections that follow the table.

Outbound	Inbound
Step 1: Create device file with dial-out or direct connect minor number for serial port. See "Creating Device Files for Serial Ports."	Step 1: Create device file with dial-in minor number for serial port. See "Creating Device Files for Serial Ports."
Step 2 (optional): Increase the number of IP tunnels if needed (16 are created by default). See "Increasing the Number of IP Tunnels."	Step 2 (optional): Increase the number of IP tunnels if needed (16 are created by default). See "Increasing the Number of IP Tunnels."
Step 3: Configure your modem. See "Configuring Your Modem."	Step 3: Configure your modem. See "Configuring Your Modem."
Step 4: Create entry in `/etc/ppp/Devices`. Optionally, add entries to `/etc/ppp/Dialers` or `Dialers.local`. See "Configuring Outbound Connections."	Step 4: Add user accounts to `/etc/passwd` to allow incoming connections. See "Configuring Inbound Connections."
Step 5: Define dial-out connection in `/etc/ppp/Systems`. See "Configuring Outbound Connections."	Step 5: Create `Login` shell script. See "Configuring Inbound Connections."
Step 6: Create `/etc/ppp/Autostart`. See "Configuring Outbound Connections."

Configuration Overview

Technical documentation

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How PPP Connections are Established

Configuration Quick Reference