Technical data

3.3.3 Pseudointerfaces
To use extended routing, you can define pseudointerfaces. A pseudointerface is
a data structure that extends subnet routing using a network interface. Each
network interface has one name and at most nine pseudointerface names. Each
network interface and pseudointerface has its own IP address, network mask, and
broadcast mask.
Like an interface, the name of an internet pseudointerface consists of three
alphabetic characters, followed by the pseudointerface unit number in the range of
0 through 255. The first two characters are the same as the two characters in the
internet interface name (interface type and interface class). The third character
identifies the controller letter that corresponds to the OpenVMS hardware
controller. For more information about interface names, refer to the Compaq
TCP/IP Services for OpenVMS Management guide.
3.4 Serial Line Connections
A serial connection is made between two systems using modems and telephone
lines or other serial lines. TCP/IP Services supports serial connections using PPP
(Point-to-Point Protocol) and SLIP (Serial Line Internet Protocol). SLIP includes
CSLIP (compressed SLIP). You can use any standard OpenVMS terminal device as
a PPP or a SLIP line. However, PPP is available for OpenVMS Alpha systems only.
One of the largest applications for IP over serial lines is dialup access. With
this type of configuration, your OpenVMS host answers calls and establishes a
connection initiated by a user on a client host. The client host can be another
OpenVMS system, a UNIX system, or a PC. Alternatively, users on your host can
originate the dialup connection to a remote host or terminal server that is running
the same protocol. Dedicated serial lines running PPP or SLIP can also be used
to connect separate LANs into a single WAN. In such a configuration, the host at
each end of the serial connection is always the same; no other hosts are allowed to
connect to either serial device.
If your OpenVMS system is part of a large network, you will probably use both
PPP and SLIP for your serial connections. As an Internet standard, PPP is often
preferred because it ensures interoperability between systems from a wide variety
of vendors. PPP provides a way for your OpenVMS Alpha system to establish a
dynamic IP network connection over a serial line without additional router or
server hardware.
SLIP has been in use for a longer period of time than PPP and is available for
most terminal servers and in most PC implementations of TCP/IP. Because SLIP
and PPP do not communicate with each other, hosts must use the same protocol
in order to communicate. For example, if your terminal server supports only
SLIP, remote hosts that connect through this server must also use SLIP. For more
information about configuring serial lines, refer to the Compaq TCP/IP Services
for OpenVMS Management guide.
For More Information
For more information about the following topics, refer to the Compaq TCP/IP
Services for OpenVMS Management guide.
• Configuring and troubleshooting OpenVMS Clusters, including load balancing
and failover configurations
• Configuring multiple interfaces and multihomed systems
• Details about pseudointerfaces
3–6 OpenVMS Server and Network Configurations