Which method is used to encapsulate IPv6 packets into IPv4?

Tunneling is the correct method used to encapsulate IPv6 packets within IPv4 packets. This process allows IPv6 packets, which may be traversing an IPv4 network, to be sent across that network by wrapping or encapsulating them in an IPv4 packet. The encapsulation effectively allows IPv6 traffic to be transmitted across IPv4 infrastructures, which is particularly important for transitioning existing networks to support IPv6.

Within the tunneling process, the original IPv6 packet is placed inside a new IPv4 packet with its own header. This mechanism is essential for maintaining communication between IPv6 endpoints across an IPv4 backbone, ensuring that the IPv6 data can traverse networks that do not directly support IPv6.

Other methods mentioned, while important in networking, do not perform this specific function of encapsulating IPv6 packets into IPv4. Bridging involves connecting two or more network segments at the data link layer and does not relate to packet encapsulation for different protocols. Fragmentation deals with splitting packets into smaller pieces to accommodate various network requirements but does not pertain to encapsulation. Lastly, routing is about determining the path that data takes through the network rather than encapsulating packets for transport.