With dual-stack implementations, while some hosts have the capability to use both the IPv4 and the IPv6 protocol stacks, they still require some help in deciding when to use the IPv6 protocol stack instead of the IPv4 protocol stack. Fortunately, this is possible using one of two methods, which are described as follows:
- The first method requires manual configuration by the user. If users know the IPv6 address of the destination IPv6 host, they can use that to establish an IPv6 session manually to that host from their dual-stack host. Although this method works well, it can become quite cumbersome to remember IPv4 and IPv6 addresses for multiple hosts.
- The second method entails using a naming service, such as DNS. With this method, the Fully Qualified Domain Names (FQDNs), such as www.howtonetwork.com, are configured using both IPv4 and IPv6 addresses. The FQDN is represented by an A record for the IPv4 protocol stack and an AAAA record for the IPv6 protocol stack, which allows the DNS server to be queried using either IPv4 or IPv6.