Final answer:
The two IPv6 addresses listed for the GigabitEthernet interfaces are part of an interface redundancy setup, which ensures high network availability by providing alternative paths for data transmission.
Step-by-step explanation:
The reason there are two IPv6 addresses listed for the GigabitEthernet interfaces is related to interface redundancy. In networking, redundancy is a key factor to ensure high availability and reliability. Each address corresponds to a separate physical interface on the router or switch, and typically, these interfaces are configured to provide redundant paths for network traffic. This configuration helps to prevent a single point of failure, meaning if one path becomes unavailable, the other can take over without disrupting network connectivity.