Which three statements are true about GRE and IP-IP tunnels? (Choose three.)
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A. B. C. D. E.ACE
GRE (Generic Routing Encapsulation) and IP-IP tunnels are both tunneling protocols used to encapsulate one protocol inside another protocol to extend a private network across an untrusted network. Here are the three statements that are true about GRE and IP-IP tunnels:
A. All intermediary devices must have reachability to the tunnel endpoints. This statement is true because GRE and IP-IP tunnels require a path from the source to the destination tunnel endpoints through intermediary devices, such as routers or switches. Therefore, all intermediary devices must be able to reach the tunnel endpoints to establish and maintain the tunnel.
C. Tunnel endpoints must have a route that directs traffic into the tunnel. This statement is true because to establish and maintain a tunnel, the tunnel endpoints must have a route that directs traffic into the tunnel. Without a route that directs traffic into the tunnel, the tunnel would not be used for forwarding packets, and the tunnel would not function as intended.
E. Tunnel endpoints require a tunnel interface. This statement is true because to create a tunnel, tunnel endpoints must have a tunnel interface. A tunnel interface is a virtual interface that represents the tunnel and is configured with tunneling parameters, such as the tunnel source and destination IP addresses, tunneling protocol, and encapsulation settings.
Statements B and D are not true about GRE and IP-IP tunnels.
B. Tunnel endpoints must use the loopback interface for reachability. This statement is not true because tunnel endpoints can use any interface for reachability, including physical interfaces, loopback interfaces, or virtual interfaces.
D. Tunnel endpoints must have a route to the remote endpoint learned by a dynamic routing protocol. This statement is not true because tunnel endpoints can learn routes to the remote endpoint through a static route, a dynamic routing protocol, or even a directly connected route. The important thing is that the tunnel endpoint has a route that directs traffic into the tunnel.