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Extend EXAMPLES section for IPv6 over GRE. Contributed by Gert Doering.

This commit is contained in:
is 2005-03-30 17:19:52 +00:00
parent 646d61aa58
commit cfb674f4eb
1 changed files with 45 additions and 2 deletions
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47
share/man/man4/gre.4
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@ -1,4 +1,4 @@
.\" $NetBSD: gre.4,v 1.29 2004/02/07 18:34:57 wiz Exp $
.\" $NetBSD: gre.4,v 1.30 2005/03/30 17:19:52 is Exp $
.\"
.\" Copyright 1998 (c) The NetBSD Foundation, Inc.
.\" All rights reserved.
@ -210,6 +210,48 @@ On router B:
Note that this is a safe situation where the link1 flag (as discussed in the
.Sx BUGS
section below) may (and probably should) be set.
.Pp
Along these lines, you can use GRE tunnels to interconnect two IPv6
networks over an IPv4 infrastructure, or to hook up to the IPv6 internet
via an IPv4 tunnel to a Cisco router.
.Bd -literal
2001:db8:1::/64 -- NetBSD A -----tunnel----- Cisco B --- IPv6 Internet
\\ /
\\ /
+----- the Internet ------+
.Ed
The example will use the following addressing: NetBSD A has the
IPv4 address A and the IPv6 address 2001:db8:1::1 (connects to internal
network 2001:db8:1::/64). Cisco B has external IPv4 address B. All
the IPv6 internet world is behind B, so A wants to route 0::0/0 (the IPv6
default route) into the tunnel. The GRE tunnel will use a transit
network: 2001:db8:ffff::1/64 on the NetBSD side, and ::2/64 on the Cisco
side.
Then the following commands will configure the tunnel:
.Pp
On router A (NetBSD):
.Bd -literal
# ifconfig greN create
# ifconfig greN inet6 2001:db8:ffff::1/64
# ifconfig greN tunnel A B
# route add -inet6 2001:db8:ffff::/64 2001:db8:ffff::2 -ifp greN
# route add -inet6 0::0/0 2001:db8:ffff::2 -ifp greN
.Ed
.Pp
On router B (Cisco):
.Bd -literal
Interface TunnelX
tunnel mode gre ip
ipv6 address 2001:db8:ffff::2/64 ! transfer network
tunnel source B ! e.g. address from LAN interface
tunnel destination A ! where the tunnel is connected to
ipv6 route 2001:db8::/64 TunnelX ! route this network through tunnel
.Ed
.Pp
Note that this is a safe situation where the link1 flag (as discussed in the
.Sx BUGS
section below) may (and probably should) be set.
.Sh NOTES
The MTU of
.Sy gre Ns Ar X
@ -223,7 +265,8 @@ For correct operation, the
device needs a route to the destination that is less specific than the
one over the tunnel.
(Basically, there needs to be a route to the decapsulating host that
does not run over the tunnel, as this would be a loop.)
does not run over the tunnel, as this would be a loop. This is not
relevant for IPv6-over-IPv4 tunnels, of course.)
If the addresses are ambiguous, doing the
.Xr ifconfig 8
.Li tunnel