Loopback address

The unicast address 0:0:0:0:0:0:0:1 is called the loopback address. It cannot be assigned to any physical or VIPA interface. It can be thought of as a link-local unicast address assigned to a virtual interface (typically called the loopback interface) that allows local applications to send messages to each other.

Restriction: The loopback address cannot be used as the source address in IPv6 packets that are sent outside of a node. An IPv6 packet with a destination address of loopback cannot be sent outside of a node and be forwarded by an IPv6 router. A packet received on an interface with destination address of loopback is dropped.