Technical data

Configuring Serial Lines
3.3 Setting Up a SLIP Interface
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 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 commands and TCP/IP management
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 the following commands:
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 the following commands:
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 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.
Configuring Serial Lines 3–13