DMVPN

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DMVPNDynamic Multipoint Virtual Private Networking

DMVPN is a dynamic VPN technology originally developed by Cisco. While their implementation was somewhat proprietary, the underlying technologies are actually standards based. The three technologies are:

  • NHRP - NBMA Next Hop Resolution Protocol (RFC2332)
  • mGRE - Multipoint Generic Routing Encapsulation / mGRE (RFC1702)
  • IPSec - IP Security (too many RFCs to list, but start with RFC4301)

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.

Baseline Configuration

STEPS:
1. Create tunnel config

  (interfaces tunnel)

2. Create nhrp

  (protocols nhrp)

3. Create ipsec vpn (optional, but recommended for security)

  (vpn ipsec)

The tunnel will be set to mGRE if for encapsulation 'gre' is set, and no 'remote-ip' is set.
If the public ip is provided by DHCP the tunnel "local-ip" can be set to "0.0.0.0"

Baseline Topology

Baseline Topology

HUB Configuration

interfaces
     tunnel <tunN> {
         address <ipv4>
         encapsulation gre
         local-ip <public ip>
         multicast enable
         description <txt>
         parameters {
             ip {
                 <usual IP options>
             }
         }
     }
 }
 protocols {
     nhrp {
         tunnel <tunN> {
             cisco-authentication <key phrase>
             holding-time <seconds>
             multicast dynamic
             redirect
         }
     }
 }
 vpn {
     ipsec {
         esp-group <text> {
             lifetime <30-86400>
             mode tunnel
             pfs enable
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption 3des
                 hash md5
             }
         }
         ike-group <text> {
             key-exchange ikev1
             lifetime <30-86400>
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption aes128
                 hash sha1
             }
         }
         ipsec-interfaces {
             interface <ethN>
         }
         profile <text> {
             authentication {
                 mode pre-shared-secret
                 pre-shared-secret <key phrase>
             }
             bind {
                 tunnel <tunN>
             }
             esp-group <text>
             ike-group <text>
         }
     }
 }

HUB Example Configuration

set interfaces ethernet eth0 address '1.1.1.1/30'
set interfaces ethernet eth1 address '192.168.1.1/24'
set system host-name 'HUB'

set interfaces tunnel tun0 address 10.0.0.1/24
set interfaces tunnel tun0 encapsulation gre
set interfaces tunnel tun0 local-ip 1.1.1.1
set interfaces tunnel tun0 multicast enable
set interfaces tunnel tun0 parameters ip key 1

set protocols nhrp tunnel tun0 cisco-authentication SECRET
set protocols nhrp tunnel tun0 holding-time  300
set protocols nhrp tunnel tun0 multicast dynamic
set protocols nhrp tunnel tun0 redirect

set vpn ipsec ipsec-interfaces interface eth0 
set vpn ipsec ike-group IKE-HUB proposal 1
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 encryption aes128 
set vpn ipsec ike-group IKE-HUB proposal 2 hash sha1 
set vpn ipsec ike-group IKE-HUB lifetime 3600
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 esp-group ESP-HUB lifetime 1800
set vpn ipsec esp-group ESP-HUB pfs dh-group2

set vpn ipsec profile NHRPVPN
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 tun0 
set vpn ipsec profile NHRPVPN esp-group ESP-HUB
set vpn ipsec profile NHRPVPN ike-group IKE-HUB

set protocols static route 0.0.0.0/0 next-hop 1.1.1.2
set protocols static route 192.168.2.0/24 next-hop 10.0.0.2
set protocols static route 192.168.3.0/24 next-hop 10.0.0.3

SPOKE1 Configuration

interfaces
     tunnel <tunN> {
         address <ipv4>
         encapsulation gre
         local-ip <public ip>
         multicast enable
         description <txt>
         parameters {
             ip {
                 <usual IP options>
             }
         }
     }
 }
 protocols {
     nhrp {
         tunnel <tunN> {
             cisco-authentication <key phrase>
             map <ipv4/net> {
                 nbma-address <ipv4>
                 register
             }
             holding-time <seconds>
             multicast nhs
             redirect
             shortcut
         }
     }
 }
 vpn {
     ipsec {
         esp-group <text> {
             lifetime <30-86400>
             mode tunnel
             pfs enable
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption 3des
                 hash md5
             }
         }
         ike-group <text> {
             key-exchange ikev1
             lifetime <30-86400>
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption aes128
                 hash sha1
             }
         }
         ipsec-interfaces {
             interface <ethN>
         }
         profile <text> {
             authentication {
                 mode pre-shared-secret
                 pre-shared-secret <key phrase>
             }
             bind {
                 tunnel <tunN>
             }
             esp-group <text>
             ike-group <text>
         }
     }
 }

SPOKE1 Example Configuration

set interfaces ethernet eth0 address 'dhcp'
set interfaces ethernet eth1 address '192.168.2.1/24'
set system host-name 'SPOKE1'

set interfaces tunnel tun0 address 10.0.0.2/24
set interfaces tunnel tun0 encapsulation gre
set interfaces tunnel tun0 local-ip 0.0.0.0
set interfaces tunnel tun0 multicast enable
set interfaces tunnel tun0 parameters ip key 1

set protocols nhrp tunnel tun0 cisco-authentication 'SECRET'
set protocols nhrp tunnel tun0 map 10.0.0.1/24 nbma-address 1.1.1.1
set protocols nhrp tunnel tun0 map 10.0.0.1/24 'register'
set protocols nhrp tunnel tun0 multicast 'nhs'
set protocols nhrp tunnel tun0 'redirect'
set protocols nhrp tunnel tun0 'shortcut'

set vpn ipsec ipsec-interfaces interface eth0 
set vpn ipsec ike-group IKE-SPOKE proposal 1
set vpn ipsec ike-group IKE-SPOKE proposal 1 encryption aes256
set vpn ipsec ike-group IKE-SPOKE proposal 1 hash sha1 
set vpn ipsec ike-group IKE-SPOKE proposal 2 encryption aes128 
set vpn ipsec ike-group IKE-SPOKE proposal 2 hash sha1 
set vpn ipsec ike-group IKE-SPOKE lifetime 3600
set vpn ipsec esp-group ESP-SPOKE proposal 1 encryption aes256 
set vpn ipsec esp-group ESP-SPOKE proposal 1 hash sha1 
set vpn ipsec esp-group ESP-SPOKE proposal 2 encryption 3des 
set vpn ipsec esp-group ESP-SPOKE proposal 2 hash md5 
set vpn ipsec esp-group ESP-SPOKE lifetime 1800
set vpn ipsec esp-group ESP-SPOKE pfs dh-group2

set vpn ipsec profile NHRPVPN
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 tun0 
set vpn ipsec profile NHRPVPN esp-group ESP-SPOKE
set vpn ipsec profile NHRPVPN ike-group IKE-SPOKE

set protocols static route 192.168.1.0/24 next-hop 10.0.0.1
set protocols static route 192.168.3.0/24 next-hop 10.0.0.3

SPOKE2 Configuration

interfaces
     tunnel <tunN> {
         address <ipv4>
         encapsulation gre
         local-ip <public ip>
         multicast enable
         description <txt>
         parameters {
             ip {
                 <usual IP options>
             }
         }
     }
 }
 protocols {
     nhrp {
         tunnel <tunN> {
             cisco-authentication <key phrase>
             map <ipv4/net> {
                 nbma-address <ipv4>
                 register
             }
             holding-time <seconds>
             multicast nhs
             redirect
             shortcut
         }
     }
 }
 vpn {
     ipsec {
         esp-group <text> {
             lifetime <30-86400>
             mode tunnel
             pfs enable
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption 3des
                 hash md5
             }
         }
         ike-group <text> {
             key-exchange ikev1
             lifetime <30-86400>
             proposal <1-65535> {
                 encryption aes256
                 hash sha1
             }
             proposal <1-65535> {
                 encryption aes128
                 hash sha1
             }
         }
         ipsec-interfaces {
             interface <ethN>
         }
         profile <text> {
             authentication {
                 mode pre-shared-secret
                 pre-shared-secret <key phrase>
             }
             bind {
                 tunnel <tunN>
             }
             esp-group <text>
             ike-group <text>
         }
     }
 }

SPOKE2 Example Configuration

set interfaces ethernet eth0 address 'dhcp'
set interfaces ethernet eth1 address '192.168.3.1/24'
set system host-name 'SPOKE2'

set interfaces tunnel tun0 address 10.0.0.3/24
set interfaces tunnel tun0 encapsulation gre
set interfaces tunnel tun0 local-ip 0.0.0.0
set interfaces tunnel tun0 multicast enable
set interfaces tunnel tun0 parameters ip key 1

set protocols nhrp tunnel tun0 cisco-authentication SECRET
set protocols nhrp tunnel tun0 map 10.0.0.1/24 nbma-address 1.1.1.1
set protocols nhrp tunnel tun0 map 10.0.0.1/24 register
set protocols nhrp tunnel tun0 multicast nhs
set protocols nhrp tunnel tun0 redirect
set protocols nhrp tunnel tun0 shortcut

set vpn ipsec ipsec-interfaces interface eth0 
set vpn ipsec ike-group IKE-SPOKE proposal 1
set vpn ipsec ike-group IKE-SPOKE proposal 1 encryption aes256
set vpn ipsec ike-group IKE-SPOKE proposal 1 hash sha1 
set vpn ipsec ike-group IKE-SPOKE proposal 2 encryption aes128 
set vpn ipsec ike-group IKE-SPOKE proposal 2 hash sha1 
set vpn ipsec ike-group IKE-SPOKE lifetime 3600
set vpn ipsec esp-group ESP-SPOKE proposal 1 encryption aes256 
set vpn ipsec esp-group ESP-SPOKE proposal 1 hash sha1 
set vpn ipsec esp-group ESP-SPOKE proposal 2 encryption 3des 
set vpn ipsec esp-group ESP-SPOKE proposal 2 hash md5 
set vpn ipsec esp-group ESP-SPOKE lifetime 1800
set vpn ipsec esp-group ESP-SPOKE pfs dh-group2

set vpn ipsec profile NHRPVPN
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 tun0 
set vpn ipsec profile NHRPVPN esp-group ESP-SPOKE
set vpn ipsec profile NHRPVPN ike-group IKE-SPOKE

set protocols static route 192.168.1.0/24 next-hop 10.0.0.1
set protocols static route 192.168.2.0/24 next-hop 10.0.0.2