Cisco Certified Network Associate (CCNA) Practice Exam

What type of IPv6 tunneling is used to tunnel over a diverse number of network layer protocols other than IPv4?

1. 6to4 tunneling

2. ISATAP tunneling

3. GRE tunneling

4. Teredo tunneling

The correct answer is: GRE tunneling

The choice of GRE tunneling is appropriate because Generic Routing Encapsulation (GRE) is designed to encapsulate a wide variety of network layer protocols inside a point-to-point connection, effectively allowing traffic from various protocols to be transmitted over a tunnel. This includes the ability to tunnel IPv6 packets over networks that may use IPv4 or other protocols, making GRE versatile for different network environments. While other tunneling methods like 6to4, ISATAP, and Teredo primarily focus on IPv6 functionality, they are somewhat limited in terms of the diversity of the underlying network protocols they can utilize. For instance, 6to4 is specifically designed for tunneling IPv6 packets over an IPv4 network, ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) is also focused on connecting IPv6 networks through IPv4, and Teredo allows IPv6 connectivity for hosts behind IPv4 NAT devices. None of these options provide the same level of flexibility as GRE when it comes to tunneling various protocols.