Calculate your IPv4 into a NAT64 synthesized IPv6 address:

Calculate IPv4 from synthesized NAT64 address:

Sample configurations for NAT64 & DNS64:

interface GigabitEthernet8
 description To internet access
 ip address
 no ip redirects
 no ip proxy-arp
 duplex auto
 speed auto
 nat64 enable
 ipv6 address FE80::2 link-local
 ipv6 address 2001:db8:20ff::2/64
 ipv6 enable
 ipv6 nd ra suppress all
interface Vlan666
 description IPv6 only clients
 no ip address
 nat64 enable
 ipv6 address FE80::1 link-local
 ipv6 address 2001:db8:666::1/64
 ipv6 enable
 ipv6 nd autoconfig default-route
ipv6 access-list NAT64
 permit ipv6 2001:db8:666::/64 64:FF9B::/96
nat64 v4 pool NAT64-IPv4
nat64 v6v4 list NAT64 pool NAT64-IPv4 overload
options {
	// other config snipped
	dns64 64:ff9b::/96 {
		clients {

Note: I've used the documentation IP ranges ( and 2001:db8::/32).