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Site-to-site IPv4 over IPv6 VPN example

In this example, two private networks with IPv4 addressing communicate securely over IPv6 infrastructure.

Example IPv4-over-IPv6 VPN topology

Configure FortiGate A interfaces

Port 2 connects to the IPv6 public network and port 3 connects to the IPv4 LAN.

config system interface

edit port2

config ipv6

set ip6-address fec0::0001:209:0fff:fe83:25f2/64

end

next

edit port3

set 192.168.2.1/24

end

Configure FortiGate A IPsec settings

The Phase 1 configuration is the same as in the IPv6 over IPv6 example.

config vpn ipsec phase1-interface

edit toB

set ip-version 6

set interface port2

set remote-gw6 fec0:0000:0000:0003:209:0fff:fe83:25c7

set dpd enable

set psksecret maryhadalittlelamb

set proposal 3des-md5 3des-sha1

end

 

The Phase 2 configuration is the same as you would use for an IPv4 VPN. By default, Phase 2 selectors are set to accept all subnet addresses for source and destination.

config vpn ipsec phase2-interface

edit toB2

set phase1name toB

set proposal 3des-md5 3des-sha1

set pfs enable

set replay enable

end

Configure FortiGate A security policies

Security policies are required to allow traffic between port3 and the IPsec interface toB in each direction. These are IPv4 security policies.

config firewall policy

edit 1

set srcintf port3

set dstintf toB

set srcaddr all

set dstaddr all

set action accept

set service ANY

set schedule always

next

edit 2

set srcintf toB

set dstintf port3

set srcaddr all

set dstaddr all

set action accept

set service ANY

set schedule always

end

Configure FortiGate A routing

This simple example requires just two static routes. Traffic to the protected network behind FortiGate B is routed via the virtual IPsec interface toB using an IPv4 static route. A default route sends all IPv6 traffic, including the IPv6 IPsec packets, out on port2.

config router static6

edit 1

set device port2

set dst 0::/0

next

edit 2

set device toB

set dst 192.168.3.0/24

end

Configure FortiGate B

The configuration of FortiGate B is very similar to that of FortiGate A. A virtual IPsec interface toA is configured on port2 and its remote gateway is the public IP address of FortiGate A. The IPsec Phase 2 configuration has IPv4 selectors.

IPv4 security policies enable traffic to pass between the private network and the IPsec interface. An IPv4 static route ensures traffic for the private network behind FortiGate A goes through the VPN and an IPv6 static route ensures that all IPv6 packets are routed to the public network.

config system interface

edit port2

config ipv6

set ip6-address fec0::0003:fe83:25c7/64

end

next

edit port3

set 192.168.3.1/24

end

config vpn ipsec phase1-interface

edit toA

set ip-version 6

set interface port2

set remote-gw6 fec0:0000:0000:0001:209:0fff:fe83:25f2

set dpd enable

set psksecret maryhadalittlelamb

set proposal 3des-md5 3des-sha1

end

config vpn ipsec phase2-interface

edit toA2

set phase1name toA

set proposal 3des-md5 3des-sha1

set pfs enable

set replay enable

end

config firewall policy

edit 1

set srcintf port3

set dstintf toA

set srcaddr all

set dstaddr all

set action accept

set service ANY

set schedule always

next

edit 2

set srcintf toA

set dstintf port3

set srcaddr all

set dstaddr all

set action accept

set service ANY

set schedule always

end

config router static6

edit 1

set device port2

set dst 0::/0

next

edit 2

set device toA

set dst 192.168.2.0/24

end