diff options
| author | kn <kn@cvs.openbsd.org> | 2021-01-08 21:26:35 +0000 |
|---|---|---|
| committer | kn <kn@cvs.openbsd.org> | 2021-01-08 21:26:35 +0000 |
| commit | bce3e94c4b5cf3d43279e6cc122a3c88d6d22476 (patch) | |
| tree | fe6b0fa1064fdb84b1f2f8f8d5698e3add62935a | |
| parent | fc2662a5afe63193e7f7532e1a6087f3bad6b21f (diff) | |
Provide "Point-to-Multipoint Layer 3 GRE tunnel interfaces (mgre) example"
From Pierre Emeriaud, thanks!
Feeback jmc
OK dlg
| -rw-r--r-- | share/man/man4/gre.4 | 65 |
1 files changed, 63 insertions, 2 deletions
diff --git a/share/man/man4/gre.4 b/share/man/man4/gre.4 index 51d75b7a590..2156c28fc8d 100644 --- a/share/man/man4/gre.4 +++ b/share/man/man4/gre.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: gre.4,v 1.80 2020/12/05 18:44:35 jmc Exp $ +.\" $OpenBSD: gre.4,v 1.81 2021/01/08 21:26:34 kn Exp $ .\" $NetBSD: gre.4,v 1.10 1999/12/22 14:55:49 kleink Exp $ .\" .\" Copyright 1998 (c) The NetBSD Foundation, Inc. @@ -28,7 +28,7 @@ .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" -.Dd $Mdocdate: December 5 2020 $ +.Dd $Mdocdate: January 8 2021 $ .Dt GRE 4 .Os .Sh NAME @@ -455,6 +455,67 @@ In most cases the following should work: .Bd -literal -offset indent pass quick on gre proto gre no state .Ed +.Ss Point-to-Multipoint Layer 3 GRE tunnel interfaces (mgre) example +.Nm mgre +can be used to build a point-to-multipoint tunnel network to several +hosts using a single +.Nm mgre +interface. +.Pp +In this example the host A has an outer IP of 198.51.100.12, host +B has 203.0.113.27, and host C has 203.0.113.254. +.Pp +Addressing within the tunnel is done using 192.0.2.0/24: +.Bd -literal + +--- Host B + / + / +Host A --- tunnel ---+ + \e + \e + +--- Host C +.Ed +.Pp +On Host A: +.Bd -literal -offset indent +# ifconfig mgreN create +# ifconfig mgreN tunneladdr 198.51.100.12 +# ifconfig mgreN inet 192.0.2.1 netmask 0xffffff00 up +.Ed +.Pp +On Host B: +.Bd -literal -offset indent +# ifconfig mgreN create +# ifconfig mgreN tunneladdr 203.0.113.27 +# ifconfig mgreN inet 192.0.2.2 netmask 0xffffff00 up +.Ed +.Pp +On Host C: +.Bd -literal -offset indent +# ifconfig mgreN create +# ifconfig mgreN tunneladdr 203.0.113.254 +# ifconfig mgreN inet 192.0.2.3 netmask 0xffffff00 up +.Ed +.Pp +To reach Host B over the tunnel (from Host A), there has to be a +route on Host A specifying the next-hop: +.Pp +.Dl # route add -host 192.0.2.2 203.0.113.27 -iface -ifp mgreN +.Pp +Similarly, to reach Host A over the tunnel from Host B, a route must +be present on B with A's outer IP as next-hop: +.Pp +.Dl # route add -host 192.0.2.1 198.51.100.12 -iface -ifp mgreN +.Pp +The same tunnel interface can then be used between host B and C by +adding the appropriate routes, making the network any-to-any instead +of hub-and-spoke: +.Pp +On Host B: +.Dl # route add -host 192.0.2.3 203.0.113.254 -iface -ifp mgreN +.Pp +On Host C: +.Dl # route add -host 192.0.2.2 203.0.113.27 -iface -ifp mgreN .Ss Point-to-Point Ethernet over GRE tunnel interfaces (egre) example .Nm egre can be used to carry Ethernet traffic between two endpoints over |