CCNA Routing and Switching (legacy) — Question 149

Which three circumstances can cause a GRE tunnel to be in an up/down state? (Choose three.)

Answer options

• A. The tunnel interface IP address is misconfigured.
• B. The tunnel source interface is down.
• C. A valid route to the destination address is missing from the routing table.
• D. The tunnel address is routed through the tunnel itself.
• E. The ISP is blocking the traffic.
• F. An ACL is blocking the outbound traffic.

Correct answer: B, C, D

Explanation

The correct answers are B, C, and D because if the tunnel source interface is down, the tunnel cannot function. Additionally, a valid route to the destination address is essential for the tunnel to operate, and routing the address through the tunnel can create a loop, causing it to fail. Options A, E, and F do not directly cause the tunnel to be in an up/down state.