Yes, it is perfectly viable to have a local area network (LAN) that operates with IPv6 while accessing the Internet via IPv4. This hybrid configuration is common due to the gradual transition from IPv4 to IPv6 and the coexistence of both protocols in different parts of the Internet and internal networks.

For this to work effectively, several strategies and technologies are used:

Dual Stack

The most direct approach is “Dual Stack”, where network devices and servers are configured to handle both IPv4 and IPv6 simultaneously. This means that each device on the network can have both an IPv4 and an IPv6 address.

Devices can communicate internally using IPv6 and use IPv4 to access services on the Internet that are not yet available in IPv6.

Tunnels

Tunnels are another option for connecting IPv6 networks to the IPv4 world. These wrap IPv6 packets inside IPv4 packets so that they can be transmitted over networks that only support IPv4.

There are several tunneling protocols, such as 6to4, 6in4 and Teredo, that can be used depending on the specific requirements and network configuration.

Network Address Translation (NAT)

Network Address Translation (NAT) for IPv6, known as NAT64, allows devices on an IPv6 network to communicate with IPv4 servers. NAT64 translates the IPv6 addresses of devices on the local network to a public IPv4 address when they access the Internet.

DNS64 is often used in conjunction with NAT64 to translate DNS responses from IPv4 to IPv6, allowing IPv6 devices to resolve domain names to IPv4 addresses.

Considerations

• Compatibility: Make sure your network equipment (routers, switches, firewalls) supports the necessary configurations to handle both protocols or the required transition technologies.
• Performance: Monitor the performance of your network and Internet connections. Some transition techniques may introduce additional latency.
• Security: Both protocols must be considered in the network security policy. Make sure security settings and devices (such as firewalls and intrusion prevention systems) are properly configured for both protocols.

The coexistence of IPv6 on LANs and IPv4 for Internet access is an important step in the transition to IPv6, facilitating a smooth migration and allowing networks to take advantage of the benefits of IPv6 internally while maintaining access to all content available in IPv4 in Internet.