142 lines
4.9 KiB
Groff
142 lines
4.9 KiB
Groff
.\" $NetBSD: ipip.4,v 1.4 2000/05/13 15:22:17 mycroft Exp $
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.\"
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.\" Copyright 1998 (c) The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Heiko W.Rupp <hwr@pilhuhn.de>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of the The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd 28 March 1999
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.Dt IPIP 4
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.Os
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.Sh NAME
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.Nm ipip
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.Nd encapsulating network device
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.Sh SYNOPSIS
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.Cd pseudo-device ipip Op Ar count
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.Sh DESCRIPTION
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The
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.Nm ipip
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network interface is a pseudo device that allows to encapsulate datagrams
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into IP. These encapsulated datagrams are routed to a destination host,
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where they are decapsulated and further routed to their final destination.
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The so called ``tunnel'' appears to the inner datagrams like one hop.
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Encapsulation is according to RFC 2003. The outer datagram header is of
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IP type 4 (IPIP).
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.Pp
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The network interfaces are named
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.Sy ipip Ns Ar 0 ,
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.Sy ipip Ns Ar 1
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and so on, as many as have given on the
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.Sy pseudo-device
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line in the system config file.
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.Pp
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Note that the IP addresses of the tunnel endpoints may be the same as the
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ones defined with
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.Xr ifconfig
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for the interface (as if IP is encapsulated), but need not be.
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.Pp
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.Sh EXAMPLE
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Configuration example:
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.Bd -literal
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Host X-- Host A ----------------tunnel---------- cisco D------Host E
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\\ |
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\\ /
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+------Host B----------Host C----------+
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.Ed
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On host A (NetBSD):
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# route add default B
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# ifconfig ipipN A D netmask 0xffffffff up
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# route add E D
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On Host D (Cisco):
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Interface TunnelX
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ip unnumbered D ! e.g. address from Ethernet interface
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tunnel source D ! e.g. address from Ethernet interface
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tunnel destination A
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ip route C <some interface and mask>
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ip route A mask C
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ip route X mask tunnelX
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OR
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On Host D (NetBSD):
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# route add default C
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# ifconfig ipipN D A
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.Pp
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If all goes well, you should see packets flowing ;-)
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.Pp
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If you want to reach Host A over the tunnel (from the Cisco D), then
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you have to have an alias on Host A for e.g. the Ethernet interface like:
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ifconfig <etherif> alias Y
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and on the cisco
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ip route Y mask tunnelX
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.Sh NOTE
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For correct operation, the
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.Nm
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device needs a route to the destination, that is less specific than the
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one over the tunnel.
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(Basically, there needs to be a route to the decapsulating host that
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does not run over the tunnel, as this would be a loop ..)
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.Pp
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In order to
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.Xr ifconfig
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to actually mark the interface as up, the keyword ``up'' must be given
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last on its command line.
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.Pp
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The kernel must be set to forward datagrams by either option
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``GATEWAY'' in the kernel config file or by issuing the appropriate
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option to
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.Xr sysctl .
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.Sh SEE ALSO
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.Xr netintro 4 ,
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.Xr ip 4 ,
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.Xr gre 4 ,
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.Xr atalk 4 ,
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.Xr inet 4 ,
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.Xr ifconfig 8 ,
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.Xr options 4 ,
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.Xr protocols 5 ,
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.Xr sysctl 8
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.Pp
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A description of IPIP encapsulation can be found in RFC 2003.
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.Sh BUGS
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The ipip_compute_route() code in ip_ipip.c toggles the last bit of the
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IP-address to provoke the search for a less specific route than the
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one directly over the tunnel to prevent loops. This is possibly not
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the best solution.
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.Pp
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Traceroute does not work yet over the tunnel :(
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