.. _size2site_ipsec:

Site-to-Site
============

Site-to-site mode provides a way to add remote peers, which could be configured
to exchange encrypted information between them and VyOS itself or
connected/routed networks.

To configure site-to-site connection you need to add peers with the
``set vpn ipsec site-to-site`` command.

You can identify a remote peer with:

* IPv4 or IPv6 address. This mode is easiest for configuration and mostly used
  when a peer has a public static IP address;
* Hostname. This mode is similar to IP address, only you define DNS name instead
  of an IP. Could be used when a peer has a public IP address and DNS name, but
  an IP address could be changed from time to time;
* Remote ID of the peer. In this mode, there is no predefined remote address
  nor DNS name of the peer. This mode is useful when a peer doesn't have a
  publicly available IP address (NAT between it and VyOS), or IP address could
  be changed.

Each site-to-site peer has the next options:

* ``authentication`` - configure authentication between VyOS and a remote peer.
  Suboptions:

 * ``id`` - ID for the local VyOS router. If defined, during the authentication
   it will be send to remote peer;

 * ``mode`` - mode for authentication between VyOS and remote peer:

  * ``pre-shared-secret`` - use predefined shared secret phrase, must be the
    same for local and remote side;

  * ``rsa`` - use simple shared RSA key. The key must be defined in the
    ``set vpn rsa-keys`` section;

  * ``x509`` - use certificates infrastructure for authentication.

 * ``pre-shared-secret`` - predefined shared secret. Used if configured
   ``mode pre-shared-secret``;

 * ``remote-id`` - define an ID for remote peer, instead of using peer name or
   address. Useful in case if the remote peer is behind NAT or if ``mode x509``
   is used;

 * ``rsa-key-name`` - shared RSA key for authentication. The key must be defined
   in the ``set vpn rsa-keys`` section;

 * ``use-x509-id`` - use local ID from x509 certificate. Cannot be used when
   ``id`` is defined;

 * ``x509`` - options for x509 authentication mode:

  * ``ca-cert-file`` - CA certificate file. Using for authenticating
    remote peer;

  * ``cert-file`` - certificate file, which will be used for authenticating
    local router on remote peer;

  * ``crl-file`` - file with the Certificate Revocation List. Using to check if
    a certificate for the remote peer is valid or revoked;

  * ``key`` - a private key, which will be used for authenticating local router
    on remote peer:

   * ``file`` - path to the key file;

   * ``password`` - passphrase private key, if needed.

* ``connection-type`` - how to handle this connection process. Possible
  variants:

 * ``initiate`` - do initial connection to remote peer immediately after
   configuring and after boot. In this mode the connection will not be restarted
   in case of disconnection, therefore should be used only together with DPD or
   another session tracking methods;

 * ``respond`` - do not try to initiate a connection to a remote peer. In this
   mode, the IPSec session will be established only after initiation from a
   remote peer. Could be useful when there is no direct connectivity to the
   peer due to firewall or NAT in the middle of the local and remote side.

* ``default-esp-group`` - ESP group to use by default for traffic encryption.
  Might be overwritten by individual settings for tunnel or VTI interface
  binding;

* ``description`` - description for this peer;

* ``dhcp-interface`` - use an IP address, received from DHCP for IPSec
  connection with this peer, instead of ``local-address``;

* ``force-encapsulation`` - force encapsulation of ESP into UDP datagrams.
  Useful in case if between local and remote side is firewall or NAT, which not
  allows passing plain ESP packets between them;

* ``ike-group`` - IKE group to use for key exchanges;

* ``ikev2-reauth`` - reauthenticate remote peer during the rekeying process.
  Can be used only with IKEv2:

 * ``yes`` - create a new IKE_SA from the scratch and try to recreate all
   IPsec SAs;

 * ``no`` - rekey without uninstalling the IPsec SAs;

 * ``inherit`` - use default behavior for the used IKE group.

* ``local-address`` - local IP address for IPSec connection with this peer.
  If defined ``any``, then an IP address which configured on interface with
  default route will be used;

* ``tunnel`` - define criteria for traffic to be matched for encrypting and send
  it to a peer:

 * ``disable`` - disable this tunnel;

 * ``esp-group`` - define ESP group for encrypt traffic, defined by this tunnel;

 * ``local`` - define a local source for match traffic, which should be
   encrypted and send to this peer:

  * ``port`` - define port. Have effect only when used together with ``prefix``;

  * ``prefix`` - IP network at local side.

 * ``protocol`` - define the protocol for match traffic, which should be
   encrypted and send to this peer;

 * ``remote`` - define the remote destination for match traffic, which should be
   encrypted and send to this peer:

  * ``port`` - define port. Have effect only when used together with ``prefix``;

  * ``prefix`` - IP network at remote side.

* ``vti`` - use a VTI interface for traffic encryption. Any traffic, which will
  be send to VTI interface will be encrypted and send to this peer. Using VTI
  makes IPSec configuration much flexible and easier in complex situation, and
  allows to dynamically add/delete remote networks, reachable via a peer, as in
  this mode router don't need to create additional SA/policy for each remote
  network:

 * ``bind`` - select a VTI interface to bind to this peer;

 * ``esp-group`` - define ESP group for encrypt traffic, passed this VTI
   interface.

Examples:
------------------

IKEv1
^^^^^

Example:

* WAN interface on `eth1`
* left subnet: `192.168.0.0/24` site1, server side (i.e. locality, actually
  there is no client or server roles)
* left local_ip: `198.51.100.3` # server side WAN IP
* right subnet: `10.0.0.0/24` site2,remote office side
* right local_ip: `203.0.113.2` # remote office side WAN IP

.. code-block:: none

  # server config
  set vpn ipsec esp-group office-srv-esp compression 'disable'
  set vpn ipsec esp-group office-srv-esp lifetime '1800'
  set vpn ipsec esp-group office-srv-esp mode 'tunnel'
  set vpn ipsec esp-group office-srv-esp pfs 'enable'
  set vpn ipsec esp-group office-srv-esp proposal 1 encryption 'aes256'
  set vpn ipsec esp-group office-srv-esp proposal 1 hash 'sha1'
  set vpn ipsec ike-group office-srv-ike ikev2-reauth 'no'
  set vpn ipsec ike-group office-srv-ike key-exchange 'ikev1'
  set vpn ipsec ike-group office-srv-ike lifetime '3600'
  set vpn ipsec ike-group office-srv-ike proposal 1 encryption 'aes256'
  set vpn ipsec ike-group office-srv-ike proposal 1 hash 'sha1'
  set vpn ipsec ipsec-interfaces interface 'eth1'
  set vpn ipsec site-to-site peer 203.0.113.2 authentication mode 'pre-shared-secret'
  set vpn ipsec site-to-site peer 203.0.113.2 authentication pre-shared-secret 'SomePreSharedKey'
  set vpn ipsec site-to-site peer 203.0.113.2 ike-group 'office-srv-ike'
  set vpn ipsec site-to-site peer 203.0.113.2 local-address '198.51.100.3'
  set vpn ipsec site-to-site peer 203.0.113.2 tunnel 0 allow-nat-networks 'disable'
  set vpn ipsec site-to-site peer 203.0.113.2 tunnel 0 allow-public-networks 'disable'
  set vpn ipsec site-to-site peer 203.0.113.2 tunnel 0 esp-group 'office-srv-esp'
  set vpn ipsec site-to-site peer 203.0.113.2 tunnel 0 local prefix '192.168.0.0/24'
  set vpn ipsec site-to-site peer 203.0.113.2 tunnel 0 remote prefix '10.0.0.0/21'

  # remote office config
  set vpn ipsec esp-group office-srv-esp compression 'disable'
  set vpn ipsec esp-group office-srv-esp lifetime '1800'
  set vpn ipsec esp-group office-srv-esp mode 'tunnel'
  set vpn ipsec esp-group office-srv-esp pfs 'enable'
  set vpn ipsec esp-group office-srv-esp proposal 1 encryption 'aes256'
  set vpn ipsec esp-group office-srv-esp proposal 1 hash 'sha1'
  set vpn ipsec ike-group office-srv-ike ikev2-reauth 'no'
  set vpn ipsec ike-group office-srv-ike key-exchange 'ikev1'
  set vpn ipsec ike-group office-srv-ike lifetime '3600'
  set vpn ipsec ike-group office-srv-ike proposal 1 encryption 'aes256'
  set vpn ipsec ike-group office-srv-ike proposal 1 hash 'sha1'
  set vpn ipsec ipsec-interfaces interface 'eth1'
  set vpn ipsec site-to-site peer 198.51.100.3 authentication mode 'pre-shared-secret'
  set vpn ipsec site-to-site peer 198.51.100.3 authentication pre-shared-secret 'SomePreSharedKey'
  set vpn ipsec site-to-site peer 198.51.100.3 ike-group 'office-srv-ike'
  set vpn ipsec site-to-site peer 198.51.100.3 local-address '203.0.113.2'
  set vpn ipsec site-to-site peer 198.51.100.3 tunnel 0 allow-nat-networks 'disable'
  set vpn ipsec site-to-site peer 198.51.100.3 tunnel 0 allow-public-networks 'disable'
  set vpn ipsec site-to-site peer 198.51.100.3 tunnel 0 esp-group 'office-srv-esp'
  set vpn ipsec site-to-site peer 198.51.100.3 tunnel 0 local prefix '10.0.0.0/21'
  set vpn ipsec site-to-site peer 198.51.100.3 tunnel 0 remote prefix '192.168.0.0/24'

Show status of new setup:

.. code-block:: none

  vyos@srv-gw0:~$ show vpn ike sa
  Peer ID / IP                            Local ID / IP
  ------------                            -------------
  203.0.113.2                                 198.51.100.3
     State  Encrypt  Hash    D-H Grp  NAT-T  A-Time  L-Time
     -----  -------  ----    -------  -----  ------  ------
     up     aes256   sha1    5        no     734     3600

  vyos@srv-gw0:~$ show vpn ipsec sa
  Peer ID / IP                            Local ID / IP
  ------------                            -------------
  203.0.113.2                                 198.51.100.3
     Tunnel  State  Bytes Out/In   Encrypt  Hash    NAT-T  A-Time  L-Time  Proto
     ------  -----  -------------  -------  ----    -----  ------  ------  -----
     0       up     7.5M/230.6K    aes256   sha1    no     567     1800    all

If there is SNAT rules on eth1, need to add exclude rule

.. code-block:: none

  # server side
  set nat source rule 10 destination address '10.0.0.0/24'
  set nat source rule 10 'exclude'
  set nat source rule 10 outbound-interface 'eth1'
  set nat source rule 10 source address '192.168.0.0/24'

  # remote office side
  set nat source rule 10 destination address '192.168.0.0/24'
  set nat source rule 10 'exclude'
  set nat source rule 10 outbound-interface 'eth1'
  set nat source rule 10 source address '10.0.0.0/24'

To allow traffic to pass through to clients, you need to add the following
rules. (if you used the default configuration at the top of this page)

.. code-block:: none

  # server side
  set firewall name OUTSIDE-LOCAL rule 32 action 'accept'
  set firewall name OUTSIDE-LOCAL rule 32 source address '10.0.0.0/24'

  # remote office side
  set firewall name OUTSIDE-LOCAL rule 32 action 'accept'
  set firewall name OUTSIDE-LOCAL rule 32 source address '192.168.0.0/24'

IKEv2
^^^^^

Imagine the following topology

.. figure:: /_static/images/vpn_s2s_ikev2.png
   :scale: 50 %
   :alt: IPSec IKEv2 site2site VPN

   IPSec IKEv2 site2site VPN (source ./draw.io/vpn_s2s_ikev2.drawio)


.. note:: Don't get confused about the used /31 tunnel subnet. :rfc:`3021`
   gives you additional information for using /31 subnets on point-to-point
   links.

**left**

.. code-block:: none

  set interfaces vti vti10 address '10.0.0.2/31'

  set vpn ipsec esp-group ESP_DEFAULT compression 'disable'
  set vpn ipsec esp-group ESP_DEFAULT lifetime '3600'
  set vpn ipsec esp-group ESP_DEFAULT mode 'tunnel'
  set vpn ipsec esp-group ESP_DEFAULT pfs 'dh-group19'
  set vpn ipsec esp-group ESP_DEFAULT proposal 10 encryption 'aes256gcm128'
  set vpn ipsec esp-group ESP_DEFAULT proposal 10 hash 'sha256'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection action 'hold'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection interval '30'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection timeout '120'
  set vpn ipsec ike-group IKEv2_DEFAULT ikev2-reauth 'no'
  set vpn ipsec ike-group IKEv2_DEFAULT key-exchange 'ikev2'
  set vpn ipsec ike-group IKEv2_DEFAULT lifetime '10800'
  set vpn ipsec ike-group IKEv2_DEFAULT mobike 'disable'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 dh-group '19'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 encryption 'aes256gcm128'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 hash 'sha256'
  set vpn ipsec ipsec-interfaces interface 'eth0.201'
  set vpn ipsec site-to-site peer 172.18.202.10 authentication id '172.18.201.10'
  set vpn ipsec site-to-site peer 172.18.202.10 authentication mode 'pre-shared-secret'
  set vpn ipsec site-to-site peer 172.18.202.10 authentication pre-shared-secret 'secretkey'
  set vpn ipsec site-to-site peer 172.18.202.10 authentication remote-id '172.18.202.10'
  set vpn ipsec site-to-site peer 172.18.202.10 connection-type 'initiate'
  set vpn ipsec site-to-site peer 172.18.202.10 ike-group 'IKEv2_DEFAULT'
  set vpn ipsec site-to-site peer 172.18.202.10 ikev2-reauth 'inherit'
  set vpn ipsec site-to-site peer 172.18.202.10 local-address '172.18.201.10'
  set vpn ipsec site-to-site peer 172.18.202.10 vti bind 'vti10'
  set vpn ipsec site-to-site peer 172.18.202.10 vti esp-group 'ESP_DEFAULT'

**right**

.. code-block:: none

  set interfaces vti vti10 address '10.0.0.3/31'

  set vpn ipsec esp-group ESP_DEFAULT compression 'disable'
  set vpn ipsec esp-group ESP_DEFAULT lifetime '3600'
  set vpn ipsec esp-group ESP_DEFAULT mode 'tunnel'
  set vpn ipsec esp-group ESP_DEFAULT pfs 'dh-group19'
  set vpn ipsec esp-group ESP_DEFAULT proposal 10 encryption 'aes256gcm128'
  set vpn ipsec esp-group ESP_DEFAULT proposal 10 hash 'sha256'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection action 'hold'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection interval '30'
  set vpn ipsec ike-group IKEv2_DEFAULT dead-peer-detection timeout '120'
  set vpn ipsec ike-group IKEv2_DEFAULT ikev2-reauth 'no'
  set vpn ipsec ike-group IKEv2_DEFAULT key-exchange 'ikev2'
  set vpn ipsec ike-group IKEv2_DEFAULT lifetime '10800'
  set vpn ipsec ike-group IKEv2_DEFAULT mobike 'disable'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 dh-group '19'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 encryption 'aes256gcm128'
  set vpn ipsec ike-group IKEv2_DEFAULT proposal 10 hash 'sha256'
  set vpn ipsec ipsec-interfaces interface 'eth0.202'
  set vpn ipsec site-to-site peer 172.18.201.10 authentication id '172.18.202.10'
  set vpn ipsec site-to-site peer 172.18.201.10 authentication mode 'pre-shared-secret'
  set vpn ipsec site-to-site peer 172.18.201.10 authentication pre-shared-secret 'secretkey'
  set vpn ipsec site-to-site peer 172.18.201.10 authentication remote-id '172.18.201.10'
  set vpn ipsec site-to-site peer 172.18.201.10 connection-type 'initiate'
  set vpn ipsec site-to-site peer 172.18.201.10 ike-group 'IKEv2_DEFAULT'
  set vpn ipsec site-to-site peer 172.18.201.10 ikev2-reauth 'inherit'
  set vpn ipsec site-to-site peer 172.18.201.10 local-address '172.18.202.10'
  set vpn ipsec site-to-site peer 172.18.201.10 vti bind 'vti10'
  set vpn ipsec site-to-site peer 172.18.201.10 vti esp-group 'ESP_DEFAULT'

Key Parameters:

* ``authentication local-id/remote-id`` - IKE identification is used for
  validation of VPN peer devices during IKE negotiation. If you do not configure
  local/remote-identity, the device uses the IPv4 or IPv6 address that
  corresponds to the local/remote peer by default.
  In certain network setups (like ipsec interface with dynamic address, or
  behind the NAT ), the IKE ID received from the peer does not match the IKE
  gateway configured on the device. This can lead to a Phase 1 validation
  failure.
  So, make sure to configure the local/remote id explicitly and ensure that the
  IKE ID is the same as the remote-identity configured on the peer device.

* ``disable-route-autoinstall`` - This option when configured disables the
  routes installed in the default table 220 for site-to-site ipsec.
  It is mostly used with VTI configuration.

* ``dead-peer-detection action = clear | hold | restart`` - R_U_THERE
  notification messages(IKEv1) or empty INFORMATIONAL messages (IKEv2)
  are periodically sent in order to check the liveliness of the IPsec peer. The
  values clear, hold, and restart all activate DPD and determine the action to
  perform on a timeout.
  With ``clear`` the connection is closed with no further actions taken.
  ``hold`` installs a trap policy, which will catch matching traffic and tries
  to re-negotiate the connection on demand.
  ``restart`` will immediately trigger an attempt to re-negotiate the
  connection.

* ``close-action = none | clear | hold | restart`` - defines the action to take
  if the remote peer unexpectedly closes a CHILD_SA (see above for meaning of
  values). A closeaction should not be used if the peer uses reauthentication or
  uniqueids.

  When the close-action option is set on the peers, the connection-type
  of each peer has to considered carefully. For example, if the option is set
  on both peers, then both would attempt to initiate and hold open multiple
  copies of each child SA. This might lead to instability of the device or
  cpu/memory utilization.

  Below flow-chart could be a quick reference for the close-action
  combination depending on how the peer is configured.

.. figure:: /_static/images/IPSec_close_action_settings.jpg

  Similar combinations are applicable for the dead-peer-detection.