Signed-off-by: Maximilian Wilhelm <max@sdn.clinic> Signed-off-by: David Sommerseth <dav...@openvpn.net> --- doc/man-sections/network-config.rst | 1 + .../virtual-routing-and-forwarding.rst | 78 +++++++++++++++++++ doc/man-sections/vpn-network-options.rst | 4 + 3 files changed, 83 insertions(+) create mode 100644 doc/man-sections/virtual-routing-and-forwarding.rst
diff --git a/doc/man-sections/network-config.rst b/doc/man-sections/network-config.rst index 12a6e960..04b30aa3 100644 --- a/doc/man-sections/network-config.rst +++ b/doc/man-sections/network-config.rst @@ -7,3 +7,4 @@ network adapter* (tun/tap device). .. include:: link-options.rst .. include:: vpn-network-options.rst +.. include:: virtual-routing-and-forwarding.rst diff --git a/doc/man-sections/virtual-routing-and-forwarding.rst b/doc/man-sections/virtual-routing-and-forwarding.rst new file mode 100644 index 00000000..28c13eee --- /dev/null +++ b/doc/man-sections/virtual-routing-and-forwarding.rst @@ -0,0 +1,78 @@ +Virtual Routing and Forwarding +------------------------------ + +Options in this section relates to configuration of virtual routing and +forwarding in combination with the underlying operating system. + +As of today this is only supported on Linux, a kernel >= 4.9 is +recommended. + +This could come in handy when for example the external network should be +only used as a means to connect to some VPN endpoints and all regular +traffic should only be routed through any tunnel(s). This could be +achieved by setting up a VRF and configuring the interface connected to +the external network to be part of the VRF. The examples below will cover +this setup. + +Another option would be to put the tun/tap interface into a VRF. This could +be done by an up-script which uses the :code:`ip link set` command shown +below. + + +VRF setup with iproute2 +``````````````````````` + +Create VRF :code:`vrf_external` and map it to routing table :code:`1023` +:: + + ip link add vrf_external type vrf table 1023 + +Move :code:`eth0` into :code:`vrf_external` +:: + + ip link set master vrf_external dev eth0 + +Any prefixes configured on :code:`eth0` will be moved from the :code`main` +routing table into routing table `1023` + + +VRF setup with ifupdown +``````````````````````` + +For Debian based Distributions :code:`ifupdown2` provides an almost drop-in +replacement for :code:`ifupdown` including VRFs and other features. +A configuration for an interface :code:`eth0` being part of VRF +code:`vrf_external` could look like this: +:: + + auto eth0 + iface eth0 + address 192.0.2.42/24 + address 2001:db8:08:15::42/64 + gateway 192.0.2.1 + gateway 2001:db8:08:15::1 + vrf vrf_external + + auto vrf_external + iface vrf_external + vrf-table 1023 + + +OpenVPN configuration +````````````````````` +The OpenVPN configuration needs to contain this line: +:: + + bind-dev vrf_external + + +Further reading +``````````````` + +Wikipedia has nice page one VRFs: https://en.wikipedia.org/wiki/Virtual_routing_and_forwarding + +This talk from the Network Track of FrOSCon 2018 provides an overview about +advanced layer 2 and layer 3 features of Linux + + - Slides: https://www.slideshare.net/BarbarossaTM/l2l3-fr-fortgeschrittene-helle-und-dunkle-magie-im-linuxnetzwerkstack + - Video (german): https://media.ccc.de/v/froscon2018-2247-l2\_l3\_fur\_fortgeschrittene\_-\_helle\_und\_dunkle\_magie\_im\_linux-netzwerkstack diff --git a/doc/man-sections/vpn-network-options.rst b/doc/man-sections/vpn-network-options.rst index 894df367..2a587c63 100644 --- a/doc/man-sections/vpn-network-options.rst +++ b/doc/man-sections/vpn-network-options.rst @@ -5,6 +5,10 @@ Options in this section relates to configuration of the virtual tun/tap network interface, including setting the VPN IP address and network routing. +--bind-dev device + (Linux only) Set ``device`` to bind the server socket to a + `Virtual Routing and Forwarding`_ device + --block-ipv6 On the client, instead of sending IPv6 packets over the VPN tunnel, all IPv6 packets are answered with an ICMPv6 no route host message. On the -- 2.26.0 _______________________________________________ Openvpn-devel mailing list Openvpn-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openvpn-devel
