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+.. _vpn-dmvpn:
+
+#####
+DMVPN
+#####
+
+:abbr:`DMVPN (Dynamic Multipoint Virtual Private Network)` is a dynamic
+:abbr:`VPN (Virtual Private Network)` technology originally developed by Cisco.
+While their implementation was somewhat proprietary, the underlying
+technologies are actually standards based. The three technologies are:
+
+* :abbr:`NHRP (Next Hop Resolution Protocol)` :rfc:`2332`
+* :abbr:`mGRE (Multipoint Generic Routing Encapsulation)` :rfc:`1702`
+* :abbr:`IPSec (IP Security)` - too many RFCs to list, but start with :rfc:`4301`
+
+NHRP provides the dynamic tunnel endpoint discovery mechanism (endpoint
+registration, and endpoint discovery/lookup), mGRE provides the tunnel
+encapsulation itself, and the IPSec protocols handle the key exchange, and
+crypto mechanism.
+
+In short, DMVPN provides the capability for creating a dynamic-mesh VPN
+network without having to pre-configure (static) all possible tunnel end-point
+peers.
+
+.. note:: DMVPN only automates the tunnel endpoint discovery and setup. A
+   complete solution also incorporates the use of a routing protocol. BGP is
+   particularly well suited for use with DMVPN.
+
+.. figure:: /_static/images/vpn_dmvpn_topology01.png
+   :scale: 40 %
+   :alt: Baseline DMVPN topology
+
+   Baseline DMVPN topology
+
+*************
+Configuration
+*************
+
+* Please refer to the :ref:`tunnel-interface` documentation for the individual
+  tunnel related options.
+
+* Please refer to the :ref:`ipsec` documentation for the individual IPSec
+  related options.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> cisco-authentication <secret>
+
+  Enables Cisco style authentication on NHRP packets. This embeds the secret
+  plaintext password to the outgoing NHRP packets. Incoming NHRP packets on
+  this interface are discarded unless the secret password is present. Maximum
+  length of the secret is 8 characters.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> dynamic-map <address>
+  nbma-domain-name <fqdn>
+
+  Specifies that the :abbr:`NBMA (Non-broadcast multiple-access network)`
+  addresses of the next hop servers are defined in the domain name
+  nbma-domain-name. For each A record opennhrp creates a dynamic NHS entry.
+
+  Each dynamic NHS will get a peer entry with the configured network address
+  and the discovered NBMA address.
+
+  The first registration request is sent to the protocol broadcast address, and
+  the server's real protocol address is dynamically detected from the first
+  registration reply.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> holding-time <timeout>
+
+  Specifies the holding time for NHRP Registration Requests and Resolution
+  Replies sent from this interface or shortcut-target. The holdtime is specified
+  in seconds and defaults to two hours.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> map cisco
+
+  If the statically mapped peer is running Cisco IOS, specify the cisco keyword.
+  It is used to fix statically the Registration Request ID so that a matching
+  Purge Request can be sent if NBMA address has changed. This is to work around
+  broken IOS which requires Purge Request ID to match the original Registration
+  Request ID.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> map nbma-address <address>
+
+  Creates static peer mapping of protocol-address to :abbr:`NBMA (Non-broadcast
+  multiple-access network)` address.
+
+  If the IP prefix mask is present, it directs opennhrp to use this peer as a
+  next hop server when sending Resolution Requests matching this subnet.
+
+  This is also known as the HUBs IP address or FQDN.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> map register
+
+  The optional parameter register specifies that Registration Request should be
+  sent to this peer on startup.
+
+  This option is required when running a DMVPN spoke.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> multicast <dynamic | nhs>
+
+  Determines how opennhrp daemon should soft switch the multicast traffic.
+  Currently, multicast traffic is captured by opennhrp daemon using a packet
+  socket, and resent back to proper destinations. This means that multicast
+  packet sending is CPU intensive.
+
+  Specfying nhs makes all multicast packets to be repeated to each statically
+  configured next hop.
+
+  Synamic instructs to forward to all peers which we have a direct connection
+  with. Alternatively, you can specify the directive multiple times for each
+  protocol-address the multicast traffic should be sent to.
+
+  .. warning:: It is very easy to misconfigure multicast repeating if you have
+    multiple NHSes.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> non-caching
+
+   Disables caching of peer information from forwarded NHRP Resolution Reply
+   packets. This can be used to reduce memory consumption on big NBMA subnets.
+
+  .. note:: Currently does not do much as caching is not implemented.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> redirect
+
+  Enable sending of Cisco style NHRP Traffic Indication packets. If this is
+  enabled and opennhrp detects a forwarded  packet, it will send a message to
+  the original sender of the packet instructing it to create a direct connection
+  with the destination. This is basically a protocol independent equivalent of
+  ICMP redirect.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> shortcut
+
+  Enable creation of shortcut routes.
+
+  A received NHRP Traffic Indication will trigger the resolution and
+  establishment of a shortcut route.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> shortcut-destination
+
+  This instructs opennhrp to reply with authorative answers on NHRP Resolution
+  Requests destinied to addresses in this interface (instead of forwarding the
+  packets). This effectively allows the creation of shortcut routes to subnets
+  located on the interface.
+
+  When specified, this should be the only keyword for the interface.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> shortcut-target <address>
+
+  Defines an off-NBMA network prefix for which the GRE interface will act as a
+  gateway. This an alternative to defining local interfaces with
+  shortcut-destination flag.
+
+.. cfgcmd:: set protocols nhrp tunnel <tunnel> shortcut-target <address>
+  holding-time <timeout>
+
+  Specifies the holding time for NHRP Registration Requests and Resolution
+  Replies sent from this interface or shortcut-target. The holdtime is specified
+  in seconds and defaults to two hours.
+
+*******
+Example
+*******
+
+
+This blueprint uses VyOS as the DMVPN Hub and Cisco (7206VXR) and VyOS as
+multiple spoke sites. The lab was build using :abbr:`EVE-NG (Emulated Virtual
+Environment NG)`.
+
+.. figure:: /_static/images/blueprint-dmvpn.png
+   :alt: DMVPN network
+
+   DMVPN example network
+
+Each node (Hub and Spoke) uses an IP address from the network 172.16.253.128/29.
+
+The below referenced IP address `192.0.2.1` is used as example address
+representing a global unicast address under which the HUB can be contacted by
+each and every individual spoke.
+
+Configuration
+=============
+
+Hub
+---
+
+.. code-block:: none
+
+  set interfaces ethernet eth0 address 192.0.2.1/24
+
+  set interfaces tunnel tun100 address '172.16.253.134/29'
+  set interfaces tunnel tun100 encapsulation 'gre'
+  set interfaces tunnel tun100 local-ip '192.0.2.1'
+  set interfaces tunnel tun100 multicast 'enable'
+  set interfaces tunnel tun100 parameters ip key '1'
+
+  set protocols nhrp tunnel tun100 cisco-authentication 'secret'
+  set protocols nhrp tunnel tun100 holding-time '300'
+  set protocols nhrp tunnel tun100 multicast 'dynamic'
+  set protocols nhrp tunnel tun100 redirect
+  set protocols nhrp tunnel tun100 shortcut
+
+  set vpn ipsec esp-group ESP-HUB compression 'disable'
+  set vpn ipsec esp-group ESP-HUB lifetime '1800'
+  set vpn ipsec esp-group ESP-HUB mode 'transport'
+  set vpn ipsec esp-group ESP-HUB pfs 'dh-group2'
+  set vpn ipsec esp-group ESP-HUB proposal 1 encryption 'aes256'
+  set vpn ipsec esp-group ESP-HUB proposal 1 hash 'sha1'
+  set vpn ipsec esp-group ESP-HUB proposal 2 encryption '3des'
+  set vpn ipsec esp-group ESP-HUB proposal 2 hash 'md5'
+  set vpn ipsec ike-group IKE-HUB ikev2-reauth 'no'
+  set vpn ipsec ike-group IKE-HUB key-exchange 'ikev1'
+  set vpn ipsec ike-group IKE-HUB lifetime '3600'
+  set vpn ipsec ike-group IKE-HUB proposal 1 dh-group '2'
+  set vpn ipsec ike-group IKE-HUB proposal 1 encryption 'aes256'
+  set vpn ipsec ike-group IKE-HUB proposal 1 hash 'sha1'
+  set vpn ipsec ike-group IKE-HUB proposal 2 dh-group '2'
+  set vpn ipsec ike-group IKE-HUB proposal 2 encryption 'aes128'
+  set vpn ipsec ike-group IKE-HUB proposal 2 hash 'sha1'
+
+  set vpn ipsec ipsec-interfaces interface 'eth0'
+
+  set vpn ipsec profile NHRPVPN authentication mode 'pre-shared-secret'
+  set vpn ipsec profile NHRPVPN authentication pre-shared-secret 'secret'
+  set vpn ipsec profile NHRPVPN bind tunnel 'tun100'
+  set vpn ipsec profile NHRPVPN esp-group 'ESP-HUB'
+  set vpn ipsec profile NHRPVPN ike-group 'IKE-HUB'
+
+.. note:: Setting this up on AWS will require a "Custom Protocol Rule" for
+  protocol number "47" (GRE) Allow Rule in TWO places. Firstly on the VPC
+  Network ACL, and secondly on the security group network ACL attached to the
+  EC2 instance. This has been tested as working for the official AMI image on
+  the AWS Marketplace. (Locate the correct VPC and security group by navigating
+  through the details pane below your EC2 instance in the AWS console).
+
+Spoke
+-----
+
+The individual spoke configurations only differ in the local IP address on the
+``tun10`` interface. See the above diagram for the individual IP addresses.
+
+spoke01-spoke04
+^^^^^^^^^^^^^^^
+
+.. code-block:: none
+
+  crypto keyring DMVPN
+    pre-shared-key address 192.0.2.1 key secret
+  !
+  crypto isakmp policy 10
+   encr aes 256
+   authentication pre-share
+   group 2
+  crypto isakmp invalid-spi-recovery
+  crypto isakmp keepalive 30 30 periodic
+  crypto isakmp profile DMVPN
+     keyring DMVPN
+     match identity address 192.0.2.1 255.255.255.255
+  !
+  crypto ipsec transform-set DMVPN-AES256 esp-aes 256 esp-sha-hmac
+   mode transport
+  !
+  crypto ipsec profile DMVPN
+   set security-association idle-time 720
+   set transform-set DMVPN-AES256
+   set isakmp-profile DMVPN
+  !
+  interface Tunnel10
+   ! individual spoke tunnel IP must change
+   ip address 172.16.253.129 255.255.255.248
+   no ip redirects
+   ip nhrp authentication secret
+   ip nhrp map 172.16.253.134 192.0.2.1
+   ip nhrp map multicast 192.0.2.1
+   ip nhrp network-id 1
+   ip nhrp holdtime 600
+   ip nhrp nhs 172.16.253.134
+   ip nhrp registration timeout 75
+   tunnel source FastEthernet0/0
+   tunnel mode gre multipoint
+   tunnel key 1
+  !
+  interface FastEthernet0/0
+   ip address dhcp
+   duplex half
+
+
+spoke05
+^^^^^^^
+
+VyOS can also run in DMVPN spoke mode.
+
+.. code-block:: none
+
+  set interfaces ethernet eth0 address 'dhcp'
+
+  set interfaces tunnel tun100 address '172.16.253.133/29'
+  set interfaces tunnel tun100 local-ip 0.0.0.0
+  set interfaces tunnel tun100 encapsulation 'gre'
+  set interfaces tunnel tun100 multicast 'enable'
+  set interfaces tunnel tun100 parameters ip key '1'
+
+  set protocols nhrp tunnel tun100 cisco-authentication 'secret'
+  set protocols nhrp tunnel tun100 holding-time '300'
+  set protocols nhrp tunnel tun100 map 172.16.253.134/29 nbma-address '192.0.2.1'
+  set protocols nhrp tunnel tun100 map 172.16.253.134/29 register
+  set protocols nhrp tunnel tun100 multicast 'nhs'
+  set protocols nhrp tunnel tun100 redirect
+  set protocols nhrp tunnel tun100 shortcut
+
+  set vpn ipsec esp-group ESP-HUB compression 'disable'
+  set vpn ipsec esp-group ESP-HUB lifetime '1800'
+  set vpn ipsec esp-group ESP-HUB mode 'transport'
+  set vpn ipsec esp-group ESP-HUB pfs 'dh-group2'
+  set vpn ipsec esp-group ESP-HUB proposal 1 encryption 'aes256'
+  set vpn ipsec esp-group ESP-HUB proposal 1 hash 'sha1'
+  set vpn ipsec esp-group ESP-HUB proposal 2 encryption '3des'
+  set vpn ipsec esp-group ESP-HUB proposal 2 hash 'md5'
+  set vpn ipsec ike-group IKE-HUB close-action 'none'
+  set vpn ipsec ike-group IKE-HUB ikev2-reauth 'no'
+  set vpn ipsec ike-group IKE-HUB key-exchange 'ikev1'
+  set vpn ipsec ike-group IKE-HUB lifetime '3600'
+  set vpn ipsec ike-group IKE-HUB proposal 1 dh-group '2'
+  set vpn ipsec ike-group IKE-HUB proposal 1 encryption 'aes256'
+  set vpn ipsec ike-group IKE-HUB proposal 1 hash 'sha1'
+  set vpn ipsec ike-group IKE-HUB proposal 2 dh-group '2'
+  set vpn ipsec ike-group IKE-HUB proposal 2 encryption 'aes128'
+  set vpn ipsec ike-group IKE-HUB proposal 2 hash 'sha1'
+
+  set vpn ipsec ipsec-interfaces interface 'eth0'
+
+  set vpn ipsec profile NHRPVPN authentication mode 'pre-shared-secret'
+  set vpn ipsec profile NHRPVPN authentication pre-shared-secret 'secret'
+  set vpn ipsec profile NHRPVPN bind tunnel 'tun100'
+  set vpn ipsec profile NHRPVPN esp-group 'ESP-HUB'
+  set vpn ipsec profile NHRPVPN ike-group 'IKE-HUB'
+
+