.\"	$NetBSD: plip.4,v 1.8 2002/02/13 08:18:01 ross Exp $
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.\" Copyright (c) 1994, 1997 Matthias Pfaller.
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.Dd December 1, 1994
.Dt PLIP 4 pc532
.Os
.Sh NAME
.Nm plip
.Nd Option for the lpt driver to allow IP over Centronics parallel ports
.Sh SYNOPSIS
.Cd "options PLIP"
.Cd "options COMPAT_PLIP10"
.Cd "options COMPAT_PLIP11"
.Sh DESCRIPTION
The
.Nm
interface provides a way to transport IP over Centronics parallel ports.
Protocols to communicate with Linux 1.0 and Linux 1.1 hosts are provided.
By default the 1.1 protocol is used.
To choose the 1.0 protocol use the link0 flag with
.Xr ifconfig 8 .
In order to use the 1.0 protocol the kernel has to be compiled with
COMPAT_PLIP10.
.Pp
The COMPAT_PLIP11 option selects a default MTU of 1486 bytes.
This is necessary to work around a bug that is present in the
.Nm
code for Linux 1.1.x and Linux 1.2.x.
.Sh NOTES
To connect two computers a "Laplink parallel cable" is used:
.sp
.TS
allbox tab(|);
c|c|c|c
l|n|n|l.
Signalname|Con A|Con B|Description
Data 0|2|15|Data out 0
Data 1|3|13|Data out 1
Data 2|4|12|Data out 2
Data 3|5|10|Data out 3/Wake out
Data 4|6|11|Data clock out
/Ack|10|5|Data in 3/Wake in
Busy|11|6|Data clock in
No Paper|12|4|Data in 2
Select|13|3|Data in 1
/Error|15|2|Data in 0
Gnd|18-25|18-25|Ground
.TE
.Pp
In both protocol versions Ethernet frames are used.
The 1.0 protocol assigns an Ethernet address of the form
FD:FD:ww:xx:yy:zz to the interface.
.Pp
The 1.1 protocol uses FC instead of FD, with ww, xx, yy and zz are
taken from the internet address ww.xx.yy.zz of the interface.
Ethernet support has to be configured into the kernel in order to use the
.Nm
interface.
.Sh DIAGNOSTICS
.Bl -diag
.It "plip?: tx hard error"
Packet transmission failed even after
.Dv PLIPMXRETRY
(20) retries.
.It "plip?: rx hard error"
.Dv PLIPMXERRS
(20) packets caused receive errors in sequence.
.It "plip?: checksum error"
A packet with a bad checksum was received.
.It "plip?: packet \*[Gt] MTU"
A bogus packet longer than the Maximum Transmission Unit (MTU)
length for the media was received.
.El
.Sh SEE ALSO
.Xr lpt 4 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Nm
interface appeared in
.Nx 1.0 .