Differentiate between multicast and anycast IPv6 addresses and give a scenario under which each of them can be used.

Multicast and Anycast are two different types of IPv6 addresses used for data transmission in networks.

1. Multicast IPv6 Addresses: Multicast addresses are used to send data to multiple destinations at the same time. They represent a group of interfaces, usually on different nodes. When a packet is sent to a multicast address, it is delivered to all interfaces that are identified by that address.

Scenario: Multicast addresses are often used in video conferencing or online gaming, where the same data needs to be sent to multiple recipients at the same time.

2. Anycast IPv6 Addresses: Anycast addresses are assigned to a group of interfaces, usually belonging to different nodes. A packet sent to an anycast address is delivered to just one of the interfaces bearing that address, typically the "nearest" one according to the routing protocol's measure of distance.

Scenario: Anycast addresses are often used in DNS systems. When a client sends a request to a DNS server, it is sent to the anycast address representing all DNS servers in a network. The request is then delivered to the nearest DNS server, reducing latency and improving load balancing.

In summary, while both multicast and anycast addresses are used to represent a group of interfaces, the key difference lies in the delivery of packets: multicast delivers to all interfaces in the group, while anycast delivers to the nearest one.