HP OpenVMS Systems Documentation
HP TCP/IP Services for OpenVMS
OpenVMS systems running TCP/IP Services communicate with other internet hosts over a variety of physical media. Because TCP/IP is independent of the underlying physical network, IP addresses are implemented in the network software, not the network hardware. (See the HP TCP/IP Services for OpenVMS Software Product Description for a complete list of supported media.)
This chapter reviews key concepts and describes:
A network controller is the hardware connection between a computer system and a physical network. Controllers perform the packet channeling to and from the physical medium of your network, usually a cable.
The network interface is a logical network controller --- a software component that communicates with your network software and the network controller.
For each interface, you can enable or disable the interface, set the
subnet mask, and assign IP and broadcast addresses.
2.2 Configuring Network Controllers
TCP/IP Services automatically recognizes network controllers at startup. If you need to change the configuration (remove, modify, or add new network controllers to your system) after installing and configuring the product, follow the installation and configuration instructions that come with your hardware; then run TCPIP$CONFIG again. The TCP/IP Services software recognizes the new controller immediately, and creates new interfaces the next time the software starts up.
Hardware installation and configuration instructions are specific for the various network controllers. Be sure to read the instructions provided with your new hardware before installing.
The configuration procedure initially configures your network interfaces. Use the following commands if you need to redefine an interface or configure serial lines. See Chapter 3 for more information about configuring serial lines.
If you are redefining an existing interface, enter the SET NOINTERFACE command before you enter the SET INTERFACE command.
Interface names include the following information:
|For this controller||Use this interface type|
|Ethernet||B, C, D, F, I, N, O, Q, R, S, W, X, Z|
|FDDI||A, C, F, Q, R, W|
|Token Ring||C, R|
|For this controller||Use this interface class|
Primary interfaces for Ethernet controllers have names in the range SE, SE0, SE1, SE2, ...SE24, SE25.
Interfaces for PPP controllers have names in the range PP, PP0, PP1, ...PP998, PP999.
Interfaces for local (loopback) controllers have names in the range LO, LO0, LO1, ...L08, L09
OpenVMS network devices are always template devices and are enumerated as FWA0, FWB0, FWC0, ...FWY0, FWZ0.
If the system has multiple interfaces, you can configure failSAFE IP to
provide automatic failover from one interface to the next. This is
useful if an interface goes offline or fails. For more information, see
2.3.2 Specifying the Network Mask
An IP address consists of a network number and a host number. The network mask is the part of the host field of the IP address the identifies the network. Every host on the same network must have the same network mask. To specify the network mask, use the /NETWORK_MASK qualifier.
TCP/IP Services calculates the default by setting:
You can also divide the host field into a site-specific network and
2.3.3 Specifying Additional IP Addresses
To establish an additional IP address for an interface, define a network alias. This can be useful when changing network numbers and you want to continue to accept packets addressed to the old interface, or for setting up a host with a single interface to act as a router between subnets. Network aliases can be added in two functionally identical ways:
$ netstat -n "-I" wf0 Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll WF0 4470 <Link> 0:0:f8:bd:bc:22 3049700 0 2976912 0 0 WF0 4470 10.10.1 10.10.1.100 3049700 0 2976912 0 0
$ ifconfig wf0 alias 10.10.2.100/24
$ netstat -n "-I" wf0 Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll WF0 4470 <Link> 0:0:f8:bd:bc:22 3049700 0 2976912 0 0 WF0 4470 10.10.1 10.10.1.100 3049700 0 2976912 0 0 WF0 4470 10.10.2 10.10.2.100 3049700 0 2976912 0 0
TCPIP> HELP IFCONFIG PARAMETERS
A serial connection is made between two systems using modems and telephone lines or other serial lines. TCP/IP Services supports serial connections using the PPP (Point-to-Point Protocol) and SLIP (Serial Line IP) protocols. SLIP includes CSLIP (compressed SLIP). You can use any standard OpenVMS terminal device as a PPP or SLIP line. (PPP is available for OpenVMS Alpha systems only.)
This chapter reviews key concepts and describes:
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 an additional router or additional server hardware.
SLIP has been in use for a longer period of time 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 wanting to
communicate must use the same protocol. For example, if your terminal
server supports only SLIP, remote hosts that connect through this
server must also use SLIP.
3.1.1 PPP and SLIP
One of the largest applications for IP over serial lines is dialup access. With this type of configuration, the 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. Or users on the host can originate the dialup connection to a remote host or terminal server 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.
3.1.2 Assigning an IP Address to Your PPP or SLIP Interface
Every network interface must have its own unique IP address. Interfaces cannot share IP addresses.
If you configure PPP interfaces for multiple remote hosts, the remote hosts can obtain their individual IP addresses from your host when they connect. Similarly, you can configure a PPP interface on your system without knowing your own IP address and obtain it when you connect to a remote system.
Before establishing SLIP communication with a remote host, however, you must obtain the IP address for the host's serial interface and assign IP addresses for each interface you configure on the local host.
When using SLIP, consider placing each serial line in a separate subnetwork. You accomplish this by assigning the same subnet mask for the interfaces at either end of the link.
SLIP sends a datagram across the serial line as a series of bytes. It uses the following characters to determine when a series of bytes should be grouped together:
|Character||Function||Hex Value||Decimal Values|
|END||Marks the end of the datagram. When the receiving SLIP encounters the END character, it knows that it has a complete datagram.||C0||192|
|ESC||Indicates the end of the SLIP control characters.||DB||219|
The SLIP starts by sending an END character. If END is encountered within the datagram as data, the SLIP inserts an escape character, sending the two-character sequence DB DC instead. If the ESC character appears within the datagram as data, it is replaced with the two-character sequence DB DD. The datagram ends with the END character after the last byte in the packet is transmitted.
There is neither a standard SLIP specification nor a defined maximum packet size for the SLIP. The TCP/IP Services implementation of SLIP accepts 1006-byte datagrams and does not send more than 1006 bytes in a datagram.
Compressed SLIP provides header compression that is beneficial for
small packets and low-speed serial links. Header compression improves
packet throughput. You can enable the CSLIP by means of the /COMPRESS
qualifier when you enter a SET INTERFACE command. See Table 3-3 for
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)
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.
|/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
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.|
In the client/server model for PPP connections, a host can function as a server, or dialup provider, to respond to incoming PPP connection requests. A host can also function as a client dialing in to a dialup provider.
For information about establishing a PPP client connection from a UNIX system, refer to the UNIX documentation. For a connection from a PC, refer to the PC's dialup networking instructions. You will need to configure your modem correctly as outlined in the Section 126.96.36.199.
Setting up an OpenVMS Alpha host as a PPP dialup provider or client involves a series of tasks. These tasks are listed in Table 3-2 in the order you should complete them, and are explained in Sections 188.8.131.52 through 184.108.40.206.
|1||Install the correct terminal driver.||Yes||Yes|
|2||Configure your modem.||Yes||Yes|
|3||Set up an asynchronous port for modem connections.||Yes||Yes|
|4||Configure an interface for a serial PPP connection.||Yes||Optional|
|5||Enable IP forwarding and dynamic routing, as appropriate.||Yes||No|
|6||Initiate a PPP connection. NETMBX and OPER privileges required.||No||Yes|
Confirm that the virtual terminal driver SYS$LOADABLE_IMAGES:SYS$TTDRIVER.EXE is installed on your host. If it is not installed, run the System Management utility (SYSMAN), connect the device, and load the driver, as shown in the following example:
$ RUN SYS$SYSTEM:SYSMAN SYSMAN> IO CONNECT VTA0 /NOADAPTER /DRIVER=SYS$TTDRIVER SYSMAN> EXIT
After you run SYSMAN, confirm that the VTA0 device was created. For more information about SYSMAN and its parameters, see the HP OpenVMS System Management Utilities Reference Manual: M-Z.
For OpenVMS Alpha Version 7.1, you must also install the ASNDRIVER remedial kit to prevent the system from crashing. To obtain the driver and associated corrections, access a remedial kit and accompanying cover letter from:
To configure the modem, follow these steps:
X = setting on (although different settings might work)
X** = setting on (required)
DTR normal X** DTR always on Verbal result codes X Numeric results codes Suppress result codes X** Display result codes Echo offline commands X No echo offline commands Auto answer on ring X** Suppress auto answer Normal carrier detect X** Carrier detect override Display all results codes X Result codes orig. mode only Disable AT command set Enable AT command set X Disconnect with +++ No disconnect with +++ X Load NVRAM defaults X Load &FO settings
DTR normal X DTR always on Verbal result codes X Numeric results codes Suppress result codes Display result codes X Echo offline commands X No echo offline commands Auto answer on ring Suppress auto answer X Normal carrier detect X Carrier detect override Display all results codes X Result codes orig. mode only Disable AT command set Enable AT command set X** Disconnect with +++ X No disconnect with +++ Load NVRAM defaults X Load &FO settings