.\"	$OpenBSD: gifconfig.8,v 1.2 1999/12/21 08:48:06 itojun Exp $
.\" 
.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
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.\"     KAME Id: gifconfig.8,v 1.1.1.1 1999/12/21 08:45:40 itojun Exp
.\"
.Dd May 17, 1998
.Dt GIFCONFIG 8
.Os
.\"
.Sh NAME
.Nm gifconfig
.Nd configure generic IP tunnel
.\"
.Sh SYNOPSIS
.Nm
.Ar interface
.Op Ar af
.Op Ar physsrc physdest
.Nm gifconfig
.Fl a
.\"
.Sh DESCRIPTION
.Nm
configures the physical address for the generic IP tunnel 
inteface, such as "gif0".
Argument
.Ar physsrc
and
.Ar physdest
are interpreted as the outer source/destination address for 
encapsulating IPv4/v6 header.
Argument
.Ar af
specifies the address family for
.Ar physsrc
and
.Ar physdest .
.Ar Af
can be
.Li inet
or 
.Li inet6 ,
and will be treated as
.Li inet
if ommitted.
.Pp
.Nm
takes the following optional argument:
.Bl -tag -width Ds
.It Fl a
Display information associated all generic IP tunnel interfaces.
.El
.Pp
Please note that it is very easy to create infinite routing loop,
when you configure tunnel over same address family
.Po
e.g. IPv4-over-IPv4
.Pc .
.\"
.Sh EXAMPLES
If you would like to configure IPv6 over IPv4
.Pq aka IPv6 in IPv4
tunnel between
.Li 10.1.1.1
and
.Li 10.2.3.4 ,
you should perform the following command:
.Bd -literal -offset
# gifconfig gif0 inet 10.1.1.1 10.2.3.4
.Ed
.Pp
.\" To use the
.\" .Li 0.0.0.0
.\" feature to establish a tunnel from host1 to host3
.\" which will encapsulate and carry packets from host2, on host1 do:
.\" .Bd -literal -offset
.\" # ifconfig gif0 inet host1  127.0.0.2  # assign an address to gif0
.\" # gifconfig gif0 inet host1 0.0.0.0    # assign encapsulation addresses
.\" # route add host2 host3 -ifp gif0:     # encap host2 packets, send to host3
.\" .Ed
.\" .Pp
.\" Note: the
.\" .Fl ifp
.\" option to route does not work as documented in
.\" most versions of FreeBSD.
.\" .Pp
.\" On host3 do:
.\" .Bd -literal -offset
.\" # ifconfig gif0 inet host3  127.0.0.2  # assign an address to gif0
.\" # gifconfig gif0 inet host3 0.0.0.0    # assign encapsulation addresses
.\" .Ed
.\" .Pp
.\" Now if you ping host2 from host1, the packets should be encapsulated
.\" with outer source address = host1 and outer destination address = host3,
.\" and delivered to host3.
.\" host3 will decapsulate the packet and deliver it normally to host2.
.\" .Pp
This is also possible to use IPv6 as outer proto, by replacing
.Li inet
to
.Li inet6 ,
and IPv4 addresses to some appropriate IPv6 addresses in above example.
.\"
.Sh RETURN VALUES
The command exits with exit status of 1 on errors, 0 on success.
.\"
.Sh SEE ALSO
.Xr gif 4 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Nm
command first appeared in WIDE Hydrangea IPv6 protocol stack kit.
.\" .Sh BUGS
.\" (to be written)