Juniper JN0-351 Exam - Topic 4 Question 43 Discussion

Actual exam question for Juniper's JN0-351 exam

Question #: 43
Topic #: 4

[All JN0-351 Questions]

Which two statements are correct about tunnels? (Choose two.)

ABFD cannot be used to monitor tunnels.

BTunnel endpoints must have a valid route to the remote tunnel endpoint.

CIP-IP tunnels are stateful.

DTunnels add additional overhead to packet size.

Show Suggested Answer

Suggested Answer: B, D

A tunnel is a connection between two computer networks, in which data is sent from one network to another through an encrypted link. Tunnels are commonly used to secure data communications between two networks or to connect two networks that use different protocols.

Option B is correct, because tunnel endpoints must have a valid route to the remote tunnel endpoint. A tunnel endpoint is the device that initiates or terminates a tunnel connection. For a tunnel to be established, both endpoints must be able to reach each other over the underlying network.This means that they must have a valid route to the IP address of the remote endpoint1.

Option D is correct, because tunnels add additional overhead to packet size. Tunnels work by encapsulating packets: wrapping packets inside of other packets. This means that the original packet becomes the payload of the surrounding packet, and the surrounding packet has its own header and trailer. The header and trailer of the surrounding packet add extra bytes to the packet size, which is called overhead.Overhead can reduce the efficiency and performance of a network, as it consumes more bandwidth and processing power2.

Option A is incorrect, because BFD can be used to monitor tunnels. BFD is a protocol that can be used to quickly detect failures in the forwarding path between two adjacent routers or switches. BFD can be integrated with various routing protocols and link aggregation protocols to provide faster convergence and fault recovery. BFD can also be used to monitor the connectivity of tunnels, such as GRE, IPsec, or MPLS.

Option C is incorrect, because IP-IP tunnels are stateless. IP-IP tunnels are a type of tunnels that use IP as both the encapsulating and encapsulated protocol. IP-IP tunnels are simple and easy to configure, but they do not provide any security or authentication features. IP-IP tunnels are stateless, which means that they do not keep track of the state or status of the tunnel connection. Stateless tunnels do not require any signaling or negotiation between the endpoints, but they also do not provide any error detection or recovery mechanisms.

1:What is Tunneling? | Tunneling in Networking2:What Is Tunnel In Networking, Its Types, And Its Benefits?: [Configuring Bidirectional Forwarding Detection] : [IP-IP Tunneling]

by Elsa at Jun 16, 2025, 07:47 PM

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Maryanne

2 months ago

Totally agree with B, routing is key for tunnel endpoints!

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Christiane

2 months ago

I thought A was true, but I guess BFD can monitor some tunnels?

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Jerilyn

3 months ago

D is spot on, tunnels do add overhead.

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Samira

3 months ago

Wait, are IP-IP tunnels really stateful? That sounds off.

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Nobuko

3 months ago

B is definitely correct, endpoints need valid routes!

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Dannie

3 months ago

I’m a bit confused about C; I thought IP-IP tunnels were stateless, but I could be wrong.

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Clement

4 months ago

I remember practicing a question similar to this, and I think D is also true since tunnels usually add some overhead.

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Matthew

4 months ago

I'm not so sure about A; I feel like I've seen something about BFD being used with tunnels in some scenarios.

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Glory

4 months ago

I think B is definitely correct because the endpoints need to communicate properly.

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Rory

4 months ago

Ah, this is a tricky one. I remember learning about tunnels, but the specifics are a bit fuzzy. I think the overhead and valid route endpoints are correct, but the other options are a bit of a mystery to me. I'll have to use my best judgment here.

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An

4 months ago

Okay, let's see here. I know tunnels add overhead, that's an easy one. And the endpoints needing a valid route also makes sense. I'm not too sure about the BFD and IP-IP tunnel details though. Guess I'll have to make an educated guess on those.

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Filiberto

5 months ago

Hmm, I'm a bit unsure about this. I remember something about tunnels and BFD, but I can't recall the details. And I'm not sure if IP-IP tunnels are stateful or not. I'll have to think this through carefully.

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Floyd

5 months ago

I'm pretty confident about this one. I know tunnels add overhead to packet size, and the endpoints need to have a valid route to each other. I'll double-check the other options, but those two seem like the clear correct answers.

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