Which two statement about GRE tunnel interface are true? (Choose two)
A. A tunnel can be established when a source the source interface is in the up/down state
B. A tunnel Destination must be Routable, but it can be unreachable
C. To establish a tunnel the source interface must be a loopback
D. To Establish a tunnel the source interface must be up/up state
E. A tunnel destination must be a physical interface that is on up/up state
Line Protocol Down Locally on the Router
Under normal circumstances, there are only three reasons for a GRE tunnel to be in the up/down state:
•There is no route, which includes the default route, to the tunnel destination address.
•The interface that anchors the tunnel source is down.
•The route to the tunnel destination address is through the tunnel itself, which results in recursion.
These three rules (missing route, interface down, and misrouted tunnel destination) are problems local to the router at the tunnel endpoints and do not cover problems in the intervening network or other features related to the GRE tunnel that might be configured. This document describes scenarios where other factors might influence the state of the GRE tunnel.
B-D
Off course BD
How can any router know if the tunnel-destination-interface is UP, it is so far for it,
🙂
Correct Answers are: BD
https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/118361-technote-gre-00.html