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NAME    [Toc]    [Back]

       slip_manual_setup  -  Describes how to manually set up the
       Serial Line Internet Protocol (SLIP)

DESCRIPTION    [Toc]    [Back]

       The Serial Line Internet Protocol  (SLIP)  is  a  protocol
       used  to run IP over serial lines, including RS-232 cables
       connecting two systems and telephone circuits. Unlike Ethernet,
  a serial line provides a point-to-point connection
       between only two hosts.  Like  Ethernet,  TCP/IP  commands
       (such  as  rlogin, ftp, and ping) can be run over the SLIP

       Note that although you do not use a network interface with
       SLIP, you must have a network interface configured on your
       system for the network daemons (such as nfsd and rwhod) to
       run  properly.   The  network interface must be configured
       with a new IP address.  For example, if you  have  a  personal
  computer that you use at home and in the office, do
       not use the same IP address for the network  interface  at
       home  as  you use in the office.  Use the netsetup utility
       for the initial SLIP configuration.  If you need to change
       the IP address, see the Changing the IP Address section in
       this reference page.

MANAGING ROUTING    [Toc]    [Back]

       You can use either the routed or the gated daemon to  manage
  routing,  if  you  are  not using the SLIP connection
       solely to communicate between the two systems  making  the

       If  you  plan  to use a system as an IP router, it must be
       configured to allow the forwarding of IP packets. For more
       information  on  setting  a system up as an IP router, see
       the  Network  Administration:   Connections   manual   and

       You  should  restart the routed or gated process if either
       was running prior configuring the SLIP interface with  the
       ifconfig  command. This ensures that the SLIP interface is
       recognized by the routed or gated daemon.


       You can use SLIP to connect systems either directly (using
       a null modem) or over telephone lines using modems.

       If  you  connect the systems directly, use an RS-232 cable
       to connect the serial ports on the two  hosts.  The  cable
       used  must be a null modem cable, such as BC22D-xx, (where
       xx varies depending on the length of the cable).

       You can use this method for hosts in  close  proximity  to
       each other.  The maximum length of this type of connection
       is defined by the RS-232 standard.

       If the systems are not in close proximity to  each  other,
       you  can  connect them using telephone line and modems. To
       use this kind of connection, attach a modem  to  a  serial
       port  on  both hosts so that the two hosts can establish a
       serial connection between them.  You  can  use  an  RS-232
       cable connected to the serial port on the host. This cable
       must be a  straight-through  cable  such  as  BC22E-xx  or
       BC22F-xx and the modems must be set to 8 bit no parity.

MODEMS    [Toc]    [Back]

       SLIP  works best when hardware control flow is used.  High
       speed modems often fall-back to a  lower  data  rate  when
       line degradation occurs.  To support hardware flow control
       you must use 25 pin connectors.


       Do not use XON/XOFF flow control.   It  will  corrupt  the
       data  stream  causing  the  TCP  layer  over  IP  to issue
       retransmit requests for over-runs.

       The modems you use with SLIP should be able  to  handle  a
       baud  rate of 38,400. If the modems you plan to use cannot
       handle a baud rate of 38,400, you should set them  to  the
       highest  baud  rate to which they can be set. For example,
       DEC V32 modems can handle baud rates up  to  19,200;  however,
  they cannot be locked at this baud rate.  The highest
 baud rate they can be set to is 9,600.

       The modems should also be  V32bis  compliant  with  V42bis
       compression.   Alternatively,  the  modems can support the
       Microcom Network Protocol (MNP), because both  V42bis  and
       MNP implement a subset of the other protocol.

       Use either the tip or kermit command to connect the modem.


       Be sure you do not have a getty  process  running  on  the
       port to which the modem is connected.

       To use the tip command, perform the following steps: Add a
       line such as the following to your /etc/remote file:


              In this example: Is the name of the  remote  system
              to  which  you want to connect.  Specifies the tty.
              Note, if you are running UUCP, tty00 is renamed  to
              ttyd0.  Specifies a baud rate of 38,400.  Specifies
              no parity.  Issue the tip  command.   For  example,
              prompt> tip REMSYS

              If  the  tip  command is successful, you get a connected
 message.  Suspend the process and return  to
              local mode.

              If you used the tip command to initiate the connection,
 issue the Ctrl/Z key sequence.  (If  you  use
              Kermit,  issue  the  Ctrl/C  followed by Ctrl/Z key
              sequence.  Enter the slattach command.   For  example:
 prompt> slattach /dev/tty00 38400 Use the ping
              command to wake up the interface on the remote system.
  For example: prompt> ping REMSYS

              It  may  take  a  few  ping messages to wake up the
              remote interface.

       Alternatively, you  can  leave  slattach  running  on  the
       remote system and rely on modem passwords and callback for

       For more information on the tip command,  see  the  tip(1)
       reference page and the Command and Shell User's Guide.

SETTING UP SLIP    [Toc]    [Back]

       To  configure your system to use SLIP, perform the following
 steps: Add the SLIP option to the host's kernel.

              By default, an entry for SLIP exists in the  system
              configuration file, /sys/conf/HOSTNAME (where HOSTNAME
 is the name of your system).


              The SLIP option is not included by default on 24 MB
              configurations systems.  On these systems, you must
              configure the SLIP option into the kernel.

              The entry appears as follows:

              options     SL

              This entry provides the host with one  SLIP  interface
 (sl0).  You can override this option by specifying
 the nslip parameter in the  /etc/sysconfigtab
              file.  For example, the following example specifies
              two SLIP interfaces (sl0 and sl1):

              net:      nslip=2

              For more information, see the section on  configuring
 the kernel in the System Administration manual.
              Add entries to the /etc/hosts file for the  network
              adapters at both ends of the SLIP network.

              For example:

              sys2_sl      sys2_sl.sl.abc.com
         hst2_sl  hst2_sl.sl.abc.com  Configure
  the SLIP interfaces by using the ifconfig command.
  For  example:  #  ifconfig  sl0

              On  hst2 , you could issue the following command: #
              ifconfig   sl0    netmask

              In  these  examples, the first argument is the name
              of the SLIP pseudodevice, the  second  argument  is
              the  local address of the SLIP interface, the third
              argument is the address of the  SLIP  interface  on
              the  remote host, and the remaining arguments specify
 the network mask.

              For more information, see the ifconfig(8) reference
              page.   Attach a serial line to a SLIP interface by
              using the slattach command.

              You use the slattach command to select  the  serial
              line  that  will be attached to the SLIP interface.
              The slattach command is also used to enable or disable
  the  SLIP  options.  For  more information on
              specifying options, see the  slattach(8)  reference

              When you use the slattach command, you do not specify
 the SLIP interface to be used  (sl0,  sl1,...).
              Instead,  the  first configured SLIP interface (one
              for which you issued an ifconfig command)  that  is
              not  already attached is used. You also specify the
              baud rate for the serial connection with the  slattach
 command. If you do not specify a rate, it uses
              the default rate of 9600 baud. The following is  an
              example  of  using the slattach command: # slattach
              tty00 9600

              In this example, tty00 attaches to a SLIP interface
              and sets the baud rate to 9600. The connection will
              use the options that were previously set. (When you
              boot the system, no SLIP options are enabled.)

              The  following  is  another example of the slattach
              command: # slattach +c -i tty00

              In this example, tty00 attaches  to a  SLIP  interface
  running at 9600 baud (the default speed). TCP
              header compression is enabled and ICMP traffic suppression
  is  disabled. (Disabling an option has no
              effect, if it was previously disabled.)

              For more information on the slattach command, refer
              to the slattach(8) reference page.

       After  completing  these steps, the SLIP network is available
 as long as the physical connection is ready  and  the
       slattach command is running. The ps command can be used to
       ensure the slattach command is running.  If  at  any  time
       the  slattach  command  exits  (due to a system or network
       error), the command can be executed again  to  reestablish
       the SLIP network.

       The  physical  connection is always ready if a direct connection
 is being used. For phone connections, the  connection
 is readied by manually dialing the modem on the local
       system to connect to the modem on the remote system.  Once
       the remote modem answers, the data/talk button (or equivalent)
 should be pressed to allow the modem  on  the  local
       host  to  assume  control of the connection.  Depending on
       the type of modem used, the connection might  take  a  few
       seconds  while the modems negotiate speeds, protocols, and
       other session parameters before it is ready for  use.  The
       connection  should  stay up until one side hangs up due to
       some error or a user intentionally disconnects by pressing
       the data/talk button.


       You  stop  the  SLIP  network by using the kill command to
       stop the running slattach  process  that  has  attached  a
       serial  line  to SLIP. You can restart the SLIP network by
       reissuing the slattach command, which readies the physical
       connection. When disabling a SLIP network that runs over a
       phone connection, press the data/talk button on the  modem
       to hang up the line.


       To change the IP addresses used on a SLIP interface do the
       following: Issue the following command to stop  the  slattach
  connection:  # kill slattach Issue the ifconfig command
 to deactivate the interface.  For example: # ifconfig
       sl0  down Issue the ifconfig command to delete the current
       local SLIP address.  For example: #  ifconfig  sl0  delete  Issue the ifconfig command to configure the
       SLIP interface.  For example: # ifconfig sl0

              In this example, is the local SLIP IP
              address and is SLIP IP address on the
              remote system to which you will connect.  Issue the
              slattach command to attach the serial line  to  the
              network interface.

SEE ALSO    [Toc]    [Back]

       Commands: ifconfig(8), netstat(1)

       Network Administration: Connections

[ Back ]
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