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Loopback encapsulation takes place when a tunnel IPv6 entry-point node encapsulates tunnel IPv6 packets originated from itself , and destined to itself . Mobile IP uses tunneling from the home agent to the mobile node 's care-of address , but rarely in the reverse direction . The entry-point node of an " inner IPv6 tunnel " receives tunnel IPv6 packets encapsulated by the " outer IPv6 tunnel " entry-point node . It provides tunnel mode semantics in the sense that the IP addresses seen by the applications and the IP addresses used on the wire are distinct from each other , providing the illusion that the application level IP addresses are tunneled over the network level IP addresses . Science and Technology Program Researchers at the Bureau of Reclamation developed and built a wireless tunnel communication system that dramatically increases the safety of tunnel inspection and maintenance crews , reduces costs , and minimizes tunnel outage times .