Technical data

Configuring Serial Lines
3.1 Key Concepts
3.1.4 Point-to-Point Protocol
PPP uses a frame format that includes a protocol field. The protocol field
identifies the protocol (for example, IP, DECnet, or OSI) to be used for
communication between the two hosts. The PPP defines the network frame
in a 5-byte header and 3-byte trailer. A PPP frame starts and ends with the
control byte 7E hex (126 decimal). The address and control bytes are constant.
The 2-byte protocol field indicates the contents of the PPP frame.
3.2 Setting Up a PPP Interface (Alpha Only)
Use the following commands to configure a PPP interface on an OpenVMS Alpha
system:
• SET INTERFACE PPn, where n is the number of the interface, takes effect
immediately and stays in effect until the next TCP/IP Services shutdown.
• SET CONFIGURATION INTERFACE PPn, where n is the number of the
interface, makes the change part of the permanent configuration and takes
effect at the next TCP/IP Services startup.
Note
Specifying PP without the interface number is equivalent to specifying
PP0.
If you enter a SHOW INTERFACE command, the address does not appear
until a PPP connection is actually established.
Table 3–1 shows the command qualifiers used for configuring PPP interfaces.
Table 3–1 Configuring PPP Interfaces
Qualifier Description
/COMPRESS=[ON|OFF|AUTOMATIC] Optional. The default is ON. Use to negotiate header
compression.
/DESTINATION=[host_name|IP_address] Optional. The default is no destination host. If you do
not specify the client host’s address, the PPP obtains
the correct address from the client host.
If the host is used as a dialup provider, use this
command to specify a unique IP address for a client.
In this case, you must also specify your host address
with the /HOST qualifier.
/HOST=[host_name | IP_address] Required when setting up a host as a dialup provider;
otherwise optional. Host name or IP address using
the interface. If your host is multihomed, specify the
unique IP address if the two IP addresses map to the
same host name.
/NETWORK_MASK=IP_address Optional. The subnet mask of the local PPP interface
in dotted-decimal notation.
/SERIAL_DEVICE=device Required for hard-wired or dedicated modem
connections. Identifies the OpenVMS device name
assigned to the PPP interface, for example, TTA1.
Configuring Serial Lines 3–3