Configure NAT64 for IPv4-Initiated Communication

IPv4-initiated communication to an IPv6 server is similar to destination NAT in an IPv4 topology. The destination IPv4 address maps to the destination IPv6 address through a one-to-one, static IP translation (not a many-to-one translation).

The firewall encodes the source IPv4 address into Well-Known Prefix 64:FF9B::/96 as defined in RFC 6052. The translated destination address is the actual IPv6 address. The use case for IPv4-initiated communication is typically when an organization is providing access from the public, untrust zone to an IPv6 server in the organization’s DMZ zone. This topology does not use a DNS64 server.

1. Enable IPv6 to operate on the firewall.
   1. Select DeviceSetupSession and edit the Session Settings.
   2. Select Enable IPv6 Firewalling.
   3. Click OK.
2. (Optional) When an IPv4 packet has its DF bit set to zero (and because IPv6 does not fragment packets), ensure the translated IPv6 packet does not exceed the path MTU for the destination IPv6 network.
   1. Select DeviceSetupSession and edit Session Settings.
   2. For NAT64 IPv6 Minimum Network MTU, enter the smallest number of bytes into which the firewall will fragment IPv4 packets for translation to IPv6 (range is 1280-9216, default is 1280).
      If you don’t want the firewall to fragment an IPv4 packet prior to translation, set the MTU to 9216. If the translated IPv6 packet still exceeds this value, the firewall drops the packet and issues an ICMP packet indicating destination unreachable - fragmentation needed.
   3. Click OK.
3. Create an address object for the IPv4 destination address (pre-translation).
   1. Select ObjectsAddresses and click Add.
   2. Enter a Name for the object, for example, nat64_ip4server.
   3. For Type, select IP Netmask and enter the IPv4 address of the firewall interface in the Untrust zone. The address must use no netmask or a netmask of /32 only. This example uses 198.51.19.1/32.
   4. Click OK.
4. Create an address object for the IPv6 source address (translated).
   1. Select ObjectsAddresses and click Add.
   2. Enter a Name for the object, for example, nat64_ip6source.
   3. For Type, select IP Netmask and enter the NAT64 IPv6 address with a netmask that is compliant with RFC 6052 (/32, /40, /48, /56, /64, or /96).
      For this example, enter 64:FF9B::/96.

      (The firewall encodes the prefix with the IPv4 source address 192.1.2.8, which is C001:0208 in hexadecimal.)
   4. Click OK.
5. Create an address object for the IPv6 destination address (translated).
   1. Select ObjectsAddresses and click Add.
   2. Enter a Name for the object, for example, nat64_server_2.
   3. For Type, select IP Netmask and enter the IPv6 address of the IPv6 server (destination). The address must use no netmask or a netmask of /128 only. This example uses 2001:DB8::2/128.
   4. Click OK.
6. Create the NAT64 rule.
   1. Select PoliciesNAT and click Add.
   2. On the General tab, enter a Name for the NAT64 rule, for example, nat64_ipv4_init.
   3. For NAT Type, select nat64.
7. Specify the original source and destination information.
   1. For the Original Packet, Add the Source Zone, likely an untrust zone.
   2. Select the Destination Zone, likely a trust or DMZ zone.
   3. For Source Address, select Any or Add the address object for the IPv4 host.
   4. For Destination Address, Add the address object for the IPv4 destination, in this example, nat64_ip4server.
   5. For Service, select any.
8. Specify the translated packet information.
   1. For the Translated Packet, in the Source Address Translation, Translation Type, select Static IP.
   2. For Translated Address, select the source translated address object you created, nat64_ip6source.
   3. For Destination Address Translation, for Translated Address, specify a single IPv6 address (the address object, in this example, nat64_server_2, or the IPv6 address of the server).
   4. Click OK.
9. Create a security policy to allow the NAT traffic from the Untrust zone.
   1. Select PoliciesSecurity and Add a rule Name.
   2. Select Source and Add a Source Zone; select Untrust.
   3. For Source Address, select Any.
   4. Select Destination and Add a Destination Zone; select DMZ.
   5. For Actions, select Allow.
   6. Click OK.
10. Commit your changes.
    Click Commit.
11. Troubleshoot or view a NAT64 session.

    > show session id <session-id>