Use the DCL command SET TERMINAL and applicable qualifiers to set up an asynchronous port for use with the modem.

• PPP dialup provider
  Enter the SET TERMINAL command and qualifiers appropriate for your modem connection. (Note that some qualifiers require LOG_IO or PHY_IO privilege, or both.) For example:

  $ SET TERMINAL TTA0: /ALTYPEAHD /AUTOBAUD /DIALUP /DISCONNECT /EIGHTBIT - _$ /MODEM /NOHANGUP /NOHOSTSYNC /NOPASTHRU /NOREADSYNCH /NOTTSYNCH - _$ /PERMANENT /TYPE_AHEAD

  
  where:

  /ALTYPEAHD	Creates a permanent, alternate type-ahead buffer. (The system parameter TTY_ALTYPADH determines the size of the type-ahead buffer.) Helpful when transferring larger files.
  /AUTOBAUD	Detects the incoming baud rate.
  /DIALUP	Specifies that the terminal is a dialup terminal.
  /DISCONNECT	Ensures that the process is disconnected if the line detects a hangup.
  /EIGHTBIT	Sets the terminal to use the 8-bit ASCII format.
  /MODEM	Specifies the use of a modem.
  /NOHANGUP	Does not hang up the modem when the client logs off. Default.
  /NOHOSTSYNC	Does not allow the use of Ctrl/S or Ctrl/Q functions from the terminal to stop or resume transmission when the input buffer is full or empty. Default.
  /PASTHRU	The terminal passes format-type data, such as carriage returns and tabs, to an application program as binary data. Default.
  /NOREADSYNCH	Does not allow the use of Ctrl/S or Ctrl/Q functions to synchronize data transmitted from the terminal. Default.
  /NOTTSYNCH	Does not allow transmission to be stopped or resumed by entering Ctrl/S or Ctrl/Q, respectively.
  /PERMANENT	Saves the settings.
  /TYPE_AHEAD	Enables remote modems. Must be set. The terminal accepts unsolicited input to the limit of the type-ahead buffer. Default.

  
  For detailed information about these and other SET TERMINAL qualifiers, see the OpenVMS DCL Dictionary: N-Z.

• PPP client (OpenVMS Alpha)
  Enter the SET TERMINAL command and qualifiers appropriate for your connection, as listed for the dialup provider, with the exception of /AUTOBAUD.
  Set the baud rates using the /SPEED=(input-rate,output-rate) qualifier. If the rates are the same, specify /SPEED=rate. For example: /SPEED=9600.

• PPP dialup provider
  Use the SET INTERFACE command and qualifiers to configure the interface for a serial PPP connection and assign a host name, IP address, network mask, and IP address for the client host, as applicable:

  TCPIP> SET INTERFACE PPn /SERIAL_DEVICE=TTn: /HOST=IP_address - _TCPIP> /NETWORK_MASK=IP_address /DESTINATION=IP_address /COMPRESS=AUTO

  
  where:

  • n is the controller name and unit number.
  • The /HOST address is the IP address.
  • The /NETWORK_MASK IP address is required if your network uses subnets.
  • The /DESTINATION address is the IP address assigned to the client host making a connection request. This address always overrides the client's own IP address, if the client has one.
  • /COMPRESS=AUTO turns off IP header compression unless the client uses it.
• PPP client (OpenVMS Alpha) (Optional)
  Use the SET INTERFACE command and /HOST qualifier to assign an IP address:

  TCPIP> SET INTERFACE PPn /SERIAL_DEVICE=TTn: /HOST=IP_address

  
  If you do not specify your host's IP address using SET INTERFACE, the dialup provider or terminal server provides an IP address after the connection is established.

  Note If the connecting client host has only a loopback and tunnel interface defined: A default route to the PPP interface is added to the routing table when the connection is established. The IP address of the PPP interface is assigned to the logical names TCPIP$INET_HOSTADDR and UCX$INET_HOSTADDR (for backward compatibility).

Enter the following command lines to enable IP forwarding:

$ sysconfig:==$SYS$SYSTEM:TCPIP$SYSCONFIG.EXE $ sysconfig -r inet ipforwarding=1 $ sysconfig -r inet ipgateway=1 $ sysconfig -q inet

To send notifications automatically on all connected LANs when new hosts or networks become reachable, use dynamic routing with the /SUPPLY option. For example, every time a PPP link is set up to a new subnetwork, RIP (Routing Information Protocol) advertises a corresponding route.

For example, enter:

TCPIP> START ROUTING /SUPPLY TCPIP> SET CONFIGURATION START ROUTING /SUPPLY

Note: If your PPP and Ethernet interfaces are in the same network, a route is created automatically for the client hosts and an ARP proxy is advertised.

3.2.1.6 Initiating a PPP Connection (OpenVMS to OpenVMS)

You use the OpenVMS PPP utility (PPPD) and associated commands to establish and manage a temporary PPP connection from an OpenVMS Alpha client host to an OpenVMS dialup provider or terminal server. Note that NETMBX and OPER privileges are required to establish a successful connection and display OPCOM messages.

To invoke PPPD, enter the DCL command PPPD. The available PPPD commands are summarized as follows. For detailed PPPD command and qualifier information, refer to the TCP/IP Networking on OpenVMS Systems manual or access online help for PPPD.

Command	Function
CONNECT	Establishes a network connection through the current physical port or a specified remote port.
DIAL_OUT	Allows direct access to a device in order to dial out over a modem or link to an external device.
DISCONNECT	Terminates the network connection and returns control to the terminal driver.
EXIT	Leaves the utility and returns you to the DCL command prompt ($).
HELP	Displays help text for PPPD commands.
SET	Determines the device and line characteristics for the specified terminal.
SHOW	Displays the device and line characteristics of the specified terminal.

To initiate a PPP connection from an OpenVMS Alpha client to an OpenVMS dialup provider or terminal server, follow these steps.

1. Confirm that you have NETMBX and OPER privileges.
2. Use the PPPD command DIAL_OUT and specify the terminal device. After the atdt prompt, enter the telephone number of the dialup provider or terminal server. (With some modems, you might need to type the number again until dialing begins.)
   For example:

   $ PPPD PPPD> DIAL_OUT TTA0 Type control-~ to send a break control-\ to disconnect control-@ to switch to a Point-to-Point connection. atdt 8671234 [Return]

3. If you are connecting to another OpenVMS system, log in to the system after you dial up, and enter the following commands to establish the connection:

   $ PPPD PPPD> CONNECT

   
   To end the connection, enter the DISCONNECT TTn command at the PPPD> prompt and log out.

4. If you are connecting to a terminal server, enter the CONNECT PPP prompt at the LOCAL> prompt. An informational message will confirm the PPP connection:

   LOCAL> CONNECT PPP [Return] Local -561- Starting SLIP or PPP datalink session %PPPD-I-CONNECTTERM, converting connection on device _TTA0: to a Point-to-Point connection

   
   To end the connection, enter DISCONNECT TTn at the PPPD> prompt. After the connection is terminated, an OPCOM message is displayed. For example:

   %%%%%%%%%%% OPCOM 23-APR-1998 15:44:32.10 %%%%%%%%%%% Message from user XYZnet on JONES %TCPIP-S-PPPDISCONN, Disconnected PPP Interface PP1 on TTA0

To remove the PPP configuration, follow these steps:

1. If you created a PPP interface, return the associated terminal port to general use. Enter:
   TCPIP> SET NOINTERFACE PPn
2. If you added special route and proxy entries with the PPP line, remove them.
3. If you changed any terminal settings in preparation for PPP, restore them. Enter the DCL command SET TERMINAL, and wait for the modem to reset and free the port and phone line.

Configuring the network interface for SLIP is equivalent to configuring the interface for Ethernet connections. In this case, the network interface is the modem connection. Remember, before configuring a SLIP line, you must choose an IP address for the interface at each end of the line and establish a physical connection.

Use the following commands to set up the SLIP interface:

• SET INTERFACE SLn takes effect immediately and stays in effect until the next product shutdown.
• SET CONFIGURATION INTERFACE SLn makes the change part of the permanent configuration. Takes effect at the next product startup.

Table 3-3 shows the command qualifiers used for configuring SLIP interfaces.

Table 3-3 Command Qualifiers Used for Configuring SLIP

Qualifier	Description
/[NO]AUTO_START	Optional. The default is /AUTO_START. Automatically creates the interface upon startup.
/COMPRESS= ON OFF AUTOMATIC	Optional. The default is No compression. Enables or disables TCP header compression (CSLIP). With /COMPRESS=AUTOMATIC, compression remains off unless the remote host begins to use it.
/[NO]FLOWCONTROL	Optional. The default is No flow control. Enables the special handling of XON and XOFF characters to work properly with modems that are configured to interpret these characters locally. Specify /FLOWCONTROL only if the host at the other end of the line is another host running DIGITAL TCP/IP Services for OpenVMS. If you cannot use /FLOWCONTROL, configure your modem to pass all the XON and XOFF characters through transparently.
/HOST=( host_name, IP_address)	Required. Host name or IP address of the local host. If your host is multihomed, you must specify an address in dotted-decimal notation.
/NETWORK_MASK= subnet_address	Required. The subnet mask of the local SLIP interface in dotted-decimal notation.
/SERIAL_DEVICE= device	Required for hard-wired or dedicated modem connections. Optional for dynamic connections. Identifies the OpenVMS device name assigned to the SLIP interface, for example, TTA1.

For example, the following command configures SLIP interface SL5, using the local IP address assigned to host CROW, with a subnetwork mask of 255.255.255.0. The interface uses the terminal device TTA3:. /COMPRESS enables TCP header compression (CSLIP). /FLOWCONTROL enables special handling of XON and XOFF characters.

TCPIP> SET INTERFACE SL5 /HOST=CROW /NETWORK_MASK=255.255.255.0 - _TCPIP> /SERIAL_DEVICE=TTA3 /COMPRESS=ON /FLOWCONTROL

3.3.1 Setting Up Hard-Wired SLIP Lines

To configure SLIP with hard-wired lines, follow these steps:

1. Establish a physical connection. Plug in a serial cable between the two host systems or ensure that they are both cabled to opposite ends of a leased line.
2. Obtain IP address as needed.
3. Configure the SLIP interface. Enter the SET INTERFACE command with the /HOST and /SERIAL_DEVICE qualifiers, which are required.

You can configure either a terminal server port or an OpenVMS system itself to answer dialin calls.

Follow these steps:

1. Configure the appropriate settings for the terminal port to which you will connect. Begin a dialog of dialing (or answering) commands with your modem. The specific required commands depend on the type of modem you are using.
   For example, to prevent the modem from hanging up when you exit the DTE session to bring up the SLIP line, enter the following:

   $ SET TERMINAL TTA2 /PERMANENT /MODEM /NOHANGUP

   
   Or, to disable interactive logins on the line, enter

   $ SET TERMINAL TTA2 /PERMANENT /NOTYPEAHEAD

   
   Any SLIP data that arrives before you enter the SET INTERFACE command is ignored. Otherwise, it triggers the creation of a new interactive login process.
   To enable interactive logins after a user sends a Break, enter:

   $ SET TERMINAL TTA2 /PERMANENT /NOAUTOBAUD /SECURE_SERVER

2. Configure the modem. Enter the appropriate commands to dial the telephone and establish communication.
3. Unless you are setting up a SLIP line between two hosts running DIGITAL TCP/IP Services for OpenVMS and plan to use the /FLOWCONTROL qualifier at both ends, disable modem recognition of XON and XOFF characters. (If SLIP packets have Ctrl/S and Ctrl/Q characters embedded in them as data, you must prevent the modem from trying to interpret them.)
   Either use hardware flow control or disable flow control entirely. The following examples disable all flow control.
   • With a DECmodem Version 3.2 in AT command mode, set:
     • AT%F0 --- No speed buffering flow control
     • AT%M0 --- Disable speed buffering (optional)
   • With a DECmodem Version 3.2 in DCML mode, set:
     • SET P2/SBU
     • SET P1/SBU
     • prompts appropriate_answers
   • With a U.S. Robotics SPORTSTER modem, set:
     • AT&B0 --- Variable, follows connection rate (optional)
     • AT&H0 --- Flow control disabled
     • AT&I0 --- Software flow control disabled
4. Obtain IP addresses as needed.
5. To dial in, follow these steps:
   1. Enter the SET HOST /DTE command:

      $ SET HOST /DTE terminal_name

   2. Type the telephone number, for example:

      ATDT telephone_number

   3. The connected system displays its interactive (command mode) prompt. You are "talking" to the terminal server and can now make the connection.

The following example shows a user named SLIP-USER at a PC named ROBIN with a 9600-baud modem, using terminal device TTA2 and connecting it to the port of a terminal server. In this example:

• The terminal server is a DECserver 700 terminal server.
• The user directs the modem to dial the telephone number 222-2222.
• The password prompt of the terminal server is #.
• The terminal server's current login password is hootowl.
• The terminal server's prompt is Local>.
• The user types Ctrl / \ (backslash) to escape from the terminal server to the SLIP host.
• The user defines interface SL2 and identifies it as SLIP device TTA1: with IP address 1.2.3.4. Communication on this line will use CSLIP.

$ SET HOST /DTE TTA2 %REM-I-TOQUIT, connection established Press Ctrl/\ to quit, Ctrl/@ for command mode ATDT 2222222 CONNECT 9600 # hootowl (not echoed) Network Access SW V1.5 for DS700-16 (c) Copyright 1994, Digital Equipment Corporation - All Rights Reserved Please type HELP if you need assistance Enter username> SLIP-USER Local> CONNECT SLIP Ctrl/\ $ TCPIP SET INTERFACE SL2 /HOST=1.2.3.4 /NETWORK_MASK=255.255.255.0 - _TCPIP> /SERIAL_DEVICE=TTA1: /COMPRESS=ON

3.3.3 Setting Up Your Host as a SLIP Dialup Provider

You can configure your host to answer calls and establish connections initiated by users on remote hosts.

To set up your host as a SLIP provider:

1. Over the line you will define as a SLIP line, dial in to the host.
2. Log in to the remote host.
3. Enter an appropriate TCPIP SET INTERFACE command, with the /SERIAL_DEVICE qualifier, to turn the line into a SLIP line.
   For example, the following command creates a SLIP interface named SL5, using the terminal device associated with the session where the command is entered.

   $ TCPIP SET INTERFACE SL5 /HOST=192.208.35.5 /SERIAL_DEVICE=TT

4. Log out.

As soon as you log out, your terminal port becomes a SLIP interface. Without causing the modem to hang up, start SLIP on the remote system.

To facilitate connection setup for end users, create a dedicated user name for each remote host that dials in. These users need to have a LOGIN.COM procedure that invokes appropriate SET TERMINAL and TCPIP SET INTERFACE commands, terminating with a LOGOUT command. Every user should specify a different SLIP interface name and host name (or IP address). These users require the OPER privilege to create interfaces.

You can enable IP forwarding on the SLIP provider host and start dynamic routing. For example, enter:

$ TCPIP SET PROTOCOL IP /FORWARD $ TCPIP SET CONFIGURATION PROTOCOL IP /FORWARD

To send notifications automatically on all connected LANs when new hosts or networks become reachable, use dynamic routing with the /SUPPLY option. For example, every time a SLIP connection is set up to a new remote subnetwork, RIP (Routing Information Protocol) advertises a corresponding route. For example, enter:

$ TCPIP START ROUTING /SUPPLY $ TCPIP SET CONFIGURATION START ROUTING /SUPPLY

3.3.4 Connecting a Host to the LAN

You can make your SLIP-connected host appear as if it were directly connected to the LAN. This is possible using a proxy ARP server --- usually the same host that is acting as a SLIP gateway into the LAN.

To use proxy ARP (Address Resolution Protocol), assign to the remote host an IP address in the same subnetwork as the LAN. As other hosts on the LAN attempt to communicate with the remote host, the SLIP gateway answers ARP queries for the remote host by giving its own LAN address. The gateway then forwards packets across the SLIP line.

Many DIGITAL DECserver terminal server products support SLIP connections and implement proxy ARP. If you dial in from an OpenVMS host to a terminal server, the terminal server automatically detects your IP address and begins responding to ARP queries, forwarding packets as necessary.

To use proxy ARP with a DECserver terminal server, assign an IP address in the same subnetwork as the terminal server.

On the terminal server, enter the SHOW PORT SLIP command. Verify that:

• A particular IP address has not already been associated with your port.
• Header compression is available, if you plan to use it.

It is also possible to set up your host as a SLIP gateway with proxy ARP. You might prefer this approach if your dialin modems are attached directly to an OpenVMS system rather than to a terminal server.

Follow these steps on the host to become a SLIP gateway:

1. Create a SLIP interface in another network or subnetwork, for example:

   $ TCPIP SET INTERFACE SL0 /HOST=10.1.2.3 /SERIAL_DEVICE=TTA2

2. Add a host route for the remote system, for example:

   $ TCPIP SET ROUTE FINCH /GATEWAY=10.1.2.3

3. Configure an ARP entry for the remote host, listing your own Ethernet address (as shown in TCPIP SHOW INTERFACE /FULL), for example:

   $ TCPIP SET ARP 08-00-2B-2C-4F-46 FINCH /PUBLIC

4. Enable IP packet forwarding, if not already done. Enter:

   $ TCPIP SET PROTOCOL IP /FORWARD

When your host is set up as a SLIP gateway, create an interface on the remote host at the other end of the serial line. Specify an address in the same subnetwork as the LAN.

Although the two ends of the SLIP line are in different subnetworks, traffic can flow properly due to the interface route you added with the SET ROUTE command.