What type of interface is a tunnel interface?

A.
sub-interface

B.
virtual interface

C.
physical interface

D.
redundant interface

Explanation:
Physical Interface – Every NetScreen firewall has some sort of physical interface.These interfaces are
used to connect the firewall to the network.
Sub Interface – Subinterfaces are used primarily with VLANs. All of the subinterfaces that are bound to a physical interface can only use the bandwidth that is provided by that interface.
Aggregate Interface – When you create an aggregate interface you are binding multiple physical interfaces
together to create one super interface.This interface acts as if it was a single physical interface. It provides cumulative bandwidth.
Redundant Interface – The redundant interface is much like the aggregate interface, but only has one of
the two benefits of the aggregate interface. Redundant interfaces are unable to combine their bandwidth, and only provide redundancy in case of a failure.This is still a great option to use when redundancy is a requirement.
VLAN 1 Interface – The redundant interface is much like the aggregate interface, but only has one of the two benefits of the aggregate interface. Redundant interfaces are unable to combine their bandwidth, and only provide redundancy in case of a failure.This is still a great option to use when redundancy is a requirement. Virtual Security Interface – This type of interface is used when two NetScreen devices are used in a high availability configuration.The two firewalls are combined to create a single entity called a virtual security device (VSD). Each device in the cluster defines a physical interface to create a VSI.This VSI has its own MAC address and IP address and operates just like a physical interface.
Management Interface – Some NetScreen firewalls contain an interface dedicated for management of the
device.This interface is called the MGT interface. It allows you to separate the management of the device from rest of the network by using this special interface. HA Interface – On NetScreen systems (NetScreen-500 and later), each device contains two HA interfaces, HA1, and HA2.These interfaces are used exclusively for high availability. One interface passes control messages to each device.The second HA interface is used for traffic synchronization. If one of the interfaces fails, the remaining HA interface would provide both services.
Tunnel Interface – A tunnel interface is used as a gateway to a VPN.This allows you to create a
VPN configuration and then bind that VPN to the tunnel interface. If you wanted to pass traffic to the VPN, you would simply create a route on your firewall to point to the tunnel interface for the remote network.The VPN will be automatically established and traffic will be encrypted and sent to the remote gateway.Tunnel interfaces are virtual and are only used for VPNs.
Loopback Interface – The loopback interface is a special interface. It is a virtual interface that does not exist
except logically inside of the firewall. A loopback interface is assigned to a zone and it is not accessible from other zones unless you specify a policy to permit the traffic. A loopback interface can be used to manage your firewall as well as to manage it.