sdn: overall language and consistency rework

[pve-docs.git] / pvesdn.adoc

[[chapter_pvesdn]]
Software-Defined Network
========================
ifndef::manvolnum[]
:pve-toplevel:
endif::manvolnum[]

The **S**oftware-**D**efined **N**etwork (SDN) feature allows you to create
virtual networks (VNets) at the datacenter level.

WARNING: SDN is currently an **experimental feature** in {pve}. This
documentation for it is also still under development. Ask on our
xref:getting_help[mailing lists or in the forum] for questions and feedback.


[[pvesdn_installation]]
Installation
------------

To enable the experimental Software-Defined Network (SDN) integration, you need
to install the `libpve-network-perl` package on every node:

----
apt update
apt install libpve-network-perl
----

NOTE: {pve} version 7 and above have the `ifupdown2` package installed by
default. If you originally installed your system with an older version, you need
to explicitly install the `ifupdown2` package.

After installation, you need to add the following line to the end of the
`/etc/network/interfaces` configuration file, so that the SDN configuration gets
included and activated.

----
source /etc/network/interfaces.d/*
----


[[pvesdn_overview]]
Overview
--------

The {pve} SDN allows for separation and fine-grained control of virtual guest
networks, using flexible, software-controlled configurations.

Separation is managed through *zones*, virtual networks (*VNets*), and
*subnets*.  A zone is its own virtually separated network area.  A VNet is a
virtual network that belongs to a zone. A subnet is an IP range inside a VNet.

Depending on the type of the zone, the network behaves differently and offers
specific features, advantages, and limitations.

Use cases for SDN range from an isolated private network on each individual node
to complex overlay networks across multiple PVE clusters on different locations.

After configuring an VNet in the cluster-wide datacenter SDN administration
interface, it is available as a common Linux bridge, locally on each node, to be
assigned to VMs and Containers.


[[pvesdn_main_configuration]]
Main Configuration
~~~~~~~~~~~~~~~~~~

Configuration is done at the web UI at datacenter level and is saved in files
located in the shared configuration file system at `/etc/pve/sdn`.

On the web interface, SDN features the following sections:

* SDN:: Here you get an overview of the current active SDN state, and you can
  apply all pending changes to the whole cluster.

* xref:pvesdn_config_zone[Zones]: Create and manage the virtually separated
  network zones

* xref:pvesdn_config_vnets[VNets] VNets: Create virtual network bridges and
  manage subnets

The Options category allows adding and managing additional services to be used
in your SDN setup.

* xref:pvesdn_config_controllers[Controllers]: For controlling layer 3 routing
  in complex setups

* xref:pvesdn_config_ipam[IPAM]: Enables external for IP address management for
  guests

* xref:pvesdn_config_dns[DNS]: Define a DNS server integration for registering
  virtual guests' hostname and IP
  addresses

[[pvesdn_config_main_sdn]]
SDN
~~~

This is the main status panel. Here you can see the deployment status of zones
on different nodes.

Pressing the 'Apply' button reloads the local configuration on all cluster
nodes.

[[pvesdn_config_zone]]
Zones
-----

A zone defines a virtually separated network. Zones are restricted to
specific nodes and assigned permissions, in order to restrict users to a certain
zone and its contained VNets.

Different technologies can be used for separation:

* Simple: Isolated Bridge. A simple layer 3 routing bridge (NAT)

* VLAN: Virtual LANs are the classic method of subdividing a LAN

* QinQ: Stacked VLAN (formally known as `IEEE 802.1ad`)

* VXLAN: Layer 2 VXLAN network via a UDP tunnel

* EVPN (BGP EVPN): VXLAN with BGP to establish Layer 3 routing


[[pvesdn_config_common_options]]
Common Options
~~~~~~~~~~~~~~

The following options are available for all zone types:

Nodes:: The nodes which the zone and associated VNets should be deployed on.

IPAM:: Use an IP Address Management (IPAM) tool to manage IPs in the
  zone. Optional, defaults to `pve`.

DNS:: DNS API server. Optional.

ReverseDNS:: Reverse DNS API server. Optional.

DNSZone:: DNS domain name. Used to register hostnames, such as
  `<hostname>.<domain>`. The DNS zone must already exist on the DNS server. Optional.


[[pvesdn_zone_plugin_simple]]
Simple Zones
~~~~~~~~~~~~

This is the simplest plugin. It will create an isolated VNet bridge.  This
bridge is not linked to a physical interface, and VM traffic is only local on
each the node.
It can be used in NAT or routed setups.


[[pvesdn_zone_plugin_vlan]]
VLAN Zones
~~~~~~~~~~

The VLAN plugin uses an existing local Linux or OVS bridge to connect to the
node's physical interface.  It uses VLAN tagging defined in the VNet to isolate
the network segments.  This allows connectivity of VMs between different nodes.

VLAN zone configuration options:

Bridge:: The local bridge or OVS switch, already configured on *each* node that
  allows node-to-node connection.


[[pvesdn_zone_plugin_qinq]]
QinQ Zones
~~~~~~~~~~

QinQ also known as VLAN stacking, that uses multiple layers of VLAN tags for
isolation.  The QinQ zone defines the outer VLAN tag (the 'Service VLAN')
whereas the inner VLAN tag is defined by the VNet.

NOTE: Your physical network switches must support stacked VLANs for this
configuration.

QinQ zone configuration options:

Bridge:: A local, VLAN-aware bridge that is already configured on each local
  node

Service VLAN:: The main VLAN tag of this zone

Service VLAN Protocol:: Allows you to choose between an 802.1q (default) or
  802.1ad service VLAN type.

MTU:: Due to the double stacking of tags, you need 4 more bytes for QinQ VLANs.
  For example, you must reduce the MTU to `1496` if you physical interface MTU is
  `1500`.


[[pvesdn_zone_plugin_vxlan]]
VXLAN Zones
~~~~~~~~~~~

The VXLAN plugin establishes a tunnel (overlay) on top of an existing network
(underlay).  This encapsulates layer 2 Ethernet frames within layer 4 UDP
datagrams using the default destination port `4789`.

You have to configure the underlay network yourself to enable UDP connectivity
between all peers.

You can, for example, create a VXLAN overlay network on top of public internet,
appearing to the VMs as if they share the same local Layer 2 network.

WARNING: VXLAN on its own does does not provide any encryption. When joining
  multiple sites via VXLAN, make sure to establish a secure connection between
  the site, for example by using a site-to-site VPN.

VXLAN zone configuration options:

Peers Address List:: A list of IP addresses of each node in the VXLAN zone. This
  can be external nodes reachable at this IP address.
  All nodes in the cluster need to be mentioned here.

MTU:: Because VXLAN encapsulation uses 50 bytes, the MTU needs to be 50 bytes
  lower than the outgoing physical interface.


[[pvesdn_zone_plugin_evpn]]
EVPN Zones
~~~~~~~~~~

The EVPN zone creates a routable Layer 3 network, capable of spanning across
multiple clusters. This is achieved by establishing a VPN and utilizing BGP as
the routing protocol.

The VNet of EVPN can have an anycast IP address and/or MAC address. The bridge
IP is the same on each node, meaning a virtual guest can use this address as
gateway.

Routing can work across VNets from different zones through a VRF (Virtual
Routing and Forwarding) interface.

EVPN zone configuration options:

VRF VXLAN ID:: A VXLAN-ID used for dedicated routing interconnect between VNets.
  It must be different than the VXLAN-ID of the VNets.

Controller:: The EVPN-controller to use for this zone. (See controller plugins
  section).

VNet MAC Address:: Anycast MAC address that gets assigned to all VNets in this
  zone.  Will be auto-generated if not defined.

Exit Nodes:: Nodes that shall be configured as exit gateways from the EVPN
  network, through the real network.  The configured nodes will announce a
  default route in the EVPN network.  Optional.

Primary Exit Node:: If you use multiple exit nodes, force traffic through this
  primary exit node, instead of load-balancing on all nodes.  Optional but
  necessary if you want to use SNAT or if your upstream router doesn't support
  ECMP.

Exit Nodes Local Routing:: This is a special option if you need to reach a VM/CT
  service from an exit node. (By default, the exit nodes only allow forwarding
  traffic between real network and EVPN network).  Optional.

Advertise Subnets:: Announce the full subnet in the EVPN network.
  If you have silent VMs/CTs (for example, if you have multiple IPs and the
  anycast gateway doesn't see traffic from theses IPs, the IP addresses won't be
  able to be reached inside the EVPN network).  Optional.

Disable ARP ND Suppression:: Don't suppress ARP or ND (Neighbor Discovery)
  packets.  This is required if you use floating IPs in your VMs (IP and MAC
  addresses are being moved between systems).  Optional.

Route-target Import:: Allows you to import a list of external EVPN route
  targets. Used for cross-DC or different EVPN network interconnects.  Optional.

MTU:: Because VXLAN encapsulation uses 50 bytes, the MTU needs to be 50 bytes
  less than the maximal MTU of the outgoing physical interface.  Optional,
  defaults to 1450.


[[pvesdn_config_vnets]]
VNets
-----

After creating a virtual network (VNet) through the SDN GUI, a local network
interface with the same name is available on each node. To connect a guest to the
VNet, assign the interface to the guest and set the IP address accordingly.

Depending on the zone, these options have different meanings and are explained
in the respective zone section in this document.

WARNING: In the current state, some options may have no effect or won't work in
certain zones.

VNet configuration options:

ID:: An up to 8 character ID to identify a VNet

Comment:: More descriptive identifier. Assigned as an alias on the interface. Optional

Zone:: The associated zone for this VNet

Tag:: The unique VLAN or VXLAN ID

VLAN Aware:: Enables vlan-aware option on the interface, enabling configuration
  in the quest.


[[pvesdn_config_subnet]]
Subnets
-------

A subnet define a specific IP range, described by the CIDR network address.
Each VNet, can have one or more subnets.

A subnet can be used to:

* Restrict the IP addresses you can define on a specific VNet
* Assign routes/gateways on a VNet in layer 3 zones
* Enable SNAT on a VNet in layer 3 zones
* Auto assign IPs on virtual guests (VM or CT) through IPAM plugins
* DNS registration through DNS plugins

If an IPAM server is associated with the subnet zone, the subnet prefix will be
automatically registered in the IPAM.

Subnet configuration options:

ID:: A CIDR network address, for example 10.0.0.0/8

Gateway:: The IP address of the network's default gateway. On layer 3 zones
  (Simple/EVPN plugins), it will be deployed on the VNet.

SNAT:: Enable Source NAT which allows VMs from inside a
  VNet to connect to the outside network by forwarding the packets to the nodes
  outgoing interface. On EVPN zones, forwarding is done on EVPN gateway-nodes.
  Optional.

DNS Zone Prefix:: Add a prefix to the domain registration, like
  <hostname>.prefix.<domain>  Optional.


[[pvesdn_config_controllers]]
Controllers
-----------

Some zones implement a separated control and data plane that require an external
external controller to manage the VNet's control plane.

Currently, only the `EVPN` zone requires an external controller.


[[pvesdn_controller_plugin_evpn]]
EVPN Controller
~~~~~~~~~~~~~~~

The `EVPN`, zone requires an external controller to manage the control plane.
The EVPN controller plugin configures the Free Range Routing (frr) router.

To enable the EVPN controller, you need to install frr on every node that shall
participate in the EVPN zone.

----
apt install frr frr-pythontools
----

EVPN controller configuration options:

ASN #:: A unique BGP ASN number. It's highly recommended to use a private ASN
  number (64512 – 65534, 4200000000 – 4294967294), as otherwise you could end up
  breaking global routing by mistake.

Peers:: An IP list of all nodes that are part of the EVPN zone.  (could also be
  external nodes or route reflector servers)


[[pvesdn_controller_plugin_BGP]]
BGP Controller
~~~~~~~~~~~~~~

The BGP controller is not used directly by a zone.
You can use it to configure FRR to manage BGP peers.

For BGP-EVPN, it can be used to define a different ASN by node, so doing EBGP.
It can also be used to export EVPN routes to an external BGP peer.

NOTE: By default, for a simple full mesh EVPN, you don't need to define a BGP
controller.

BGP controller configuration options:

Node:: The node of this BGP controller

ASN #:: A unique BGP ASN number. It's highly recommended to use a private ASN
  number in the range (64512 - 65534) or (4200000000 - 4294967294), as otherwise
  you could break global routing by mistake.

Peer:: A list of peer IP addresses you want to communicate with using the
  underlying BGP network.

EBGP:: If your peer's remote-AS is different, this enables EBGP.

Loopback Interface:: Use a loopback or dummy interface as the source of the EVPN network
  (for multipath).

ebgp-mutltihop:: Increase the number of hops to reach peers, in case they are
  not directly connected or they use loopback.

bgp-multipath-as-path-relax:: Allow ECMP if your peers have different ASN.


[[pvesdn_controller_plugin_ISIS]]
ISIS Controller
~~~~~~~~~~~~~~~

The ISIS controller is not used directly by a zone.
You can use it to configure FRR to export EVPN routes to an ISIS domain.

ISIS controller configuration options:

Node:: The node of this ISIS controller.

Domain:: A unique ISIS domain.

Network Entity Title:: A Unique ISIS network address that identifies this node.

Interfaces:: A list of physical interface(s) used by ISIS.

Loopback:: Use a loopback or dummy interface as the source of the EVPN network
  (for multipath).


[[pvesdn_config_ipam]]
IPAM
----

IP Address Management (IPAM) tools manage the IP addresses of clients on the
network. SDN in {pve} uses IPAM for example to find free IP addresses for new
guests.

A single IPAM instance can be associated with one or more zones.


[[pvesdn_ipam_plugin_pveipam]]
PVE IPAM Plugin
~~~~~~~~~~~~~~~

The default built-in IPAM for your {pve} cluster.


[[pvesdn_ipam_plugin_netbox]]
NetBox IPAM Plugin
~~~~~~~~~~~~~

link:https://github.com/netbox-community/netbox[NetBox] is an open-source IP
Address Management (IPAM) and datacenter infrastructure management (DCIM) tool.

To integrate NetBox with {pve} SDN, create an API token in NetBox as described
here: https://docs.netbox.dev/en/stable/integrations/rest-api/#tokens

The NetBox configuration properties are:

URL:: The NetBox REST API endpoint: `http://yournetbox.domain.com/api`

Token:: An API access token


[[pvesdn_ipam_plugin_phpipam]]
phpIPAM Plugin
~~~~~~~~~~~~~~

In link:https://phpipam.net/[phpIPAM] you need to create an "application" and add
an API token with admin privileges to the application.

The phpIPAM configuration properties are:

URL:: The REST-API endpoint: `http://phpipam.domain.com/api/<appname>/`

Token:: An API access token

Section:: An integer ID. Sections are a group of subnets in phpIPAM. Default
  installations use `sectionid=1` for customers.


[[pvesdn_config_dns]]
DNS
---

The DNS plugin in {pve} SDN is used to define a DNS API server for registration
of your hostname and IP address. A DNS configuration is associated with one or
more zones, to provide DNS registration for all the subnet IPs configured for
a zone.

[[pvesdn_dns_plugin_powerdns]]
PowerDNS Plugin
~~~~~~~~~~~~~~~
https://doc.powerdns.com/authoritative/http-api/index.html

You need to enable the web server and the API in your PowerDNS config:

----
api=yes
api-key=arandomgeneratedstring
webserver=yes
webserver-port=8081
----

The PowerDNS configuration options are:

url:: The REST API endpoint: http://yourpowerdnserver.domain.com:8081/api/v1/servers/localhost

key:: An API access key

ttl:: The default TTL for records


[[pvesdn_setup_examples]]
Examples
--------

This section presents multiple configuration examples tailored for common SDN
use cases. It aims to offer tangible implementations, providing additional
details to enhance comprehension of the available configuration options.


[[pvesdn_setup_example_simple]]
Simple Zone Example
~~~~~~~~~~~~~~~~~~~

Simple zone networks create an isolated network for quests on a single host to
connect to each other.

TIP: connection between quests are possible if all quests reside on a same host
but cannot be reached on other nodes.

* Create a simple zone named `simple`.
* Add a VNet names `vnet1`.
* Create a Subnet with a gateway and the SNAT option enabled.
* This creates a network bridge `vnet1` on the node. Assign this bridge to the
  quests that shall join the network and configure an IP address.

The network interface configuration in two VMs may look like this which allows
them to communicate via the 10.0.1.0/24 network.

----
allow-hotplug ens19
iface ens19 inet static
	address 10.0.1.14/24
----

----
allow-hotplug ens19
iface ens19 inet static
	address 10.0.1.15/24
----


[[pvesdn_setup_example_nat]]
Source NAT Example
~~~~~~~~~~~~~~~~~~

If you want to allow outgoing connections for quests in the simple network zone
the simple zone offers a Source NAT (SNAT) option.

Starting from the configuration xref:pvesdn_setup_example_simple[above], Add a
Subnet to the VNet `vnet1`, set a gateway IP and enable the SNAT option.

----
Subnet: 172.16.0.0/24
Gateway: 172.16.0.1
SNAT: checked
----

In the quests configure the static IP address inside the subnet's IP range.

The node itself will join this network with the Gateway IP '172.16.0.1' and
function as the NAT gateway for quests within the subnet range.


[[pvesdn_setup_example_vlan]]
VLAN Setup Example
~~~~~~~~~~~~~~~~~~

When VMs on different nodes need to communicate through an isolated network, the
VLAN zone allows network level isolation using VLAN tags.

Create a VLAN zone named `myvlanzone`:

----
ID: myvlanzone
Bridge: vmbr0
----

Create a VNet named `myvnet1` with VLAN tag 10 and the previously created
`myvlanzone`.

----
ID: myvnet1
Zone: myvlanzone
Tag: 10
----

Apply the configuration through the main SDN panel, to create VNets locally on
each node.

Create a Debian-based virtual machine ('vm1') on node1, with a vNIC on `myvnet1`.

Use the following network configuration for this VM:

----
auto eth0
iface eth0 inet static
	address 10.0.3.100/24
----

Create a second virtual machine ('vm2') on node2, with a vNIC on the same VNet
`myvnet1` as vm1.

Use the following network configuration for this VM:

----
auto eth0
iface eth0 inet static
	address 10.0.3.101/24
----

Following this, you should be able to ping between both VMs using that network.


[[pvesdn_setup_example_qinq]]
QinQ Setup Example
~~~~~~~~~~~~~~~~~~


This example configures two QinQ zones and adds two VMs to each zone to
demonstrate the additional layer of VLAN tags which allows the configuration of
more isolated VLANs.

A typical use case for this configuration is a hosting provider that provides an
isolated network to customers for VM communication but isolates the VMs from
other customers.

Create a QinQ zone named `qinqzone1` with service VLAN 20

----
ID: qinqzone1
Bridge: vmbr0
Service VLAN: 20
----

Create another QinQ zone named `qinqzone2` with service VLAN 30
----
ID: qinqzone2
Bridge: vmbr0
Service VLAN: 30
----

Create a VNet named `myvnet1` with VLAN-ID 100 on the previously created
`qinqzone1` zone.

----
ID: qinqvnet1
Zone: qinqzone1
Tag: 100
----

Create a `myvnet2` with VLAN-ID 100 on the  `qinqzone2` zone.

----
ID: qinqvnet2
Zone: qinqzone2
Tag: 100
----

Apply the configuration on the main SDN web-interface panel to create VNets
locally on each node.

Create four Debian-bases virtual machines (vm1, vm2, vm3, vm4) and add network
interfaces to vm1 and vm2 with bridge `qinqvnet1` and vm3 and vm4 with bridge
`qinqvnet2`.

Inside the VM, configure the IP addresses of the interfaces, for example via
`/etc/network/interfaces`:

----
auto eth0
iface eth0 inet static
	address 10.0.3.101/24
----
// TODO: systemd-network example
Configure all four VMs to have IP addresses from the '10.0.3.101' to
'10.0.3.104' range.

Now you should be able to ping between the VMs 'vm1' and 'vm2', as well as
between 'vm3' and 'vm4'. However, neither of VMs 'vm1' or 'vm2' can ping VMs
'vm3' or 'vm4', as they are on a different zone with a different service-VLAN.


[[pvesdn_setup_example_vxlan]]
VXLAN Setup Example
~~~~~~~~~~~~~~~~~~~

The example assumes a cluster with three nodes, with the node IP addresses
192.168.0.1, 192.168.0.2 and 192.168.0.3.

Create a VXLAN zone named `myvxlanzone` and add all IPs from the nodes to the
peer address list. Use the default MTU of 1450 or configure accordingly.

----
ID: myvxlanzone
Peers Address List: 192.168.0.1,192.168.0.2,192.168.0.3
----

Create a VNet named `vxvnet1` using the VXLAN zone `myvxlanzone` created
previously.

----
ID: vxvnet1
Zone: myvxlanzone
Tag: 100000
----

Apply the configuration on the main SDN web-interface panel to create VNets
locally on each nodes.

Create a Debian-based virtual machine ('vm1') on node1, with a vNIC on `vxvnet1`.

Use the following network configuration for this VM (note the lower MTU).

----
auto eth0
iface eth0 inet static
	address 10.0.3.100/24
	mtu 1450
----

Create a second virtual machine ('vm2') on node3, with a vNIC on the same VNet
`vxvnet1` as vm1.

Use the following network configuration for this VM:

----
auto eth0
iface eth0 inet static
	address 10.0.3.101/24
	mtu 1450
----

Then, you should be able to ping between between 'vm1' and 'vm2'.


[[pvesdn_setup_example_evpn]]
EVPN Setup Example
~~~~~~~~~~~~~~~~~~

The example assumes a cluster with three nodes (node1, node2, node3) with IP
addresses 192.168.0.1, 192.168.0.2 and 192.168.0.3.

Create an EVPN controller, using a private ASN number and the above node
addresses as peers.

----
ID: myevpnctl
ASN#: 65000
Peers: 192.168.0.1,192.168.0.2,192.168.0.3
----

Create an EVPN zone named `myevpnzone`, assign the previously created
EVPN-controller and define 'node1' and 'node2' as exit nodes.

----
ID: myevpnzone
VRF VXLAN Tag: 10000
Controller: myevpnctl
MTU: 1450
VNet MAC Address: 32:F4:05:FE:6C:0A
Exit Nodes: node1,node2
----

Create the first VNet named `myvnet1` using the EVPN zone `myevpnzone`.

----
ID: myvnet1
Zone: myevpnzone
Tag: 11000
----

Create a subnet on `myvnet1`:

----
Subnet: 10.0.1.0/24
Gateway: 10.0.1.1
----

Create the second VNet named `myvnet2` using the same EVPN zone `myevpnzone`.

----
ID: myvnet2
Zone: myevpnzone
Tag: 12000
----

Create a different subnet on `myvnet2``:

----
Subnet: 10.0.2.0/24
Gateway: 10.0.2.1
----

Apply the configuration from the main SDN web-interface panel to create VNets
locally on each node and generate the FRR configuration.

Create a Debian-based virtual machine ('vm1') on node1, with a vNIC on `myvnet1`.

Use the following network configuration for 'vm1':

----
auto eth0
iface eth0 inet static
	address 10.0.1.100/24
	gateway 10.0.1.1
	mtu 1450
----

Create a second virtual machine ('vm2') on node2, with a vNIC on the other VNet
`myvnet2`.

Use the following network configuration for 'vm2':

----
auto eth0
iface eth0 inet static
	address 10.0.2.100/24
	gateway 10.0.2.1
	mtu 1450
----


Now you should be able to ping vm2 from vm1, and vm1 from vm2.

If you ping an external IP from 'vm2' on the non-gateway node3, the packet
will go to the configured 'myvnet2' gateway, then will be routed to the exit
nodes ('node1' or 'node2') and from there it will leave those nodes over the
default gateway configured on node1 or node2.

NOTE: You need to add reverse routes for the '10.0.1.0/24' and '10.0.2.0/24'
networks to node1 and node2 on your external gateway, so that the public network
can reply back.

If you have configured an external BGP router, the BGP-EVPN routes (10.0.1.0/24
and 10.0.2.0/24 in this example), will be announced dynamically.


[[pvesdn_notes]]
Notes
-----

Multiple EVPN Exit Nodes
~~~~~~~~~~~~~~~~~~~~~~~~

If you have multiple gateway nodes, you should disable the `rp_filter` (Strict
Reverse Path Filter) option, because packets can arrive at one node but go out
from another node.

Add the following to `/etc/sysctl.conf`:

-----
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.all.rp_filter=0
-----

VXLAN IPSEC Encryption
~~~~~~~~~~~~~~~~~~~~~~

To add IPSEC encryption on top of a VXLAN, this example shows how to use
`strongswan`.

You`ll need to reduce the 'MTU' by additional 60 bytes for IPv4 or 80 bytes for
IPv6 to handle encryption.

So with default real 1500 MTU, you need to use a MTU of 1370 (1370 + 80 (IPSEC)
+ 50 (VXLAN) == 1500).

Install strongswan on the host.

----
apt install strongswan
----

Add configuration to `/etc/ipsec.conf`. We only need to encrypt traffic from
the VXLAN UDP port '4789'.

----
conn %default
    ike=aes256-sha1-modp1024!  # the fastest, but reasonably secure cipher on modern HW
    esp=aes256-sha1!
    leftfirewall=yes           # this is necessary when using Proxmox VE firewall rules

conn output
    rightsubnet=%dynamic[udp/4789]
    right=%any
    type=transport
    authby=psk
    auto=route

conn input
    leftsubnet=%dynamic[udp/4789]
    type=transport
    authby=psk
    auto=route
----

Generate a pre-shared key with:

----
openssl rand -base64 128
----

and add the key to `/etc/ipsec.secrets`, so that the file contents looks like:

----
: PSK <generatedbase64key>
----

Copy the PSK and the configuration to all nodes participating in the VXLAN network.