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Question 35 of 497

Implementing hybrid interconnectivity →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is a BGP configuration mismatch between Cloud Router and the on-premises router for the IDLE peer. This is correct because the IDLE state in BGP indicates that the session has never successfully established, and when one peer is ESTABLISHED while another remains IDLE, the most likely cause is a mismatch in fundamental BGP parameters—such as the AS number, peer IP address, or MD5 authentication—specific to that failing peer. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of BGP session states and common troubleshooting steps; a common trap is assuming the IDLE peer is caused by a network reachability issue when the real problem is a configuration error on one side. For a memory tip, remember that IDLE means “I Don’t Like the Establishment” parameters—check the ASN, peer IP, and authentication first.

PCNE Implementing hybrid interconnectivity Practice Question

This PCNE practice question tests your understanding of implementing hybrid interconnectivity. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Exhibit

Refer to the exhibit.

```
$ gcloud compute routers get-status router-1 --region=us-central1
kind: compute#routerStatus
result:
  bgpPeerStatus:
  - name: peer-1
    ipAddress: 169.254.1.1
    peerIpAddress: 169.254.1.2
    status: ESTABLISHED
    routesLearned: 120
  - name: peer-2
    ipAddress: 169.254.2.1
    peerIpAddress: 169.254.2.2
    status: IDLE
    routesLearned: 0
  bestRoutesForRouter:
  - dest: 10.0.0.0/8
    nextHop: 169.254.1.2
    priority: 100
  - dest: 10.0.0.0/8
    nextHop: 169.254.2.2
    priority: 200
```

Refer to the exhibit. The Cloud Router shows one BGP peer as ESTABLISHED and one as IDLE. The best routes show two routes to the same destination with different priorities. What is the most likely reason the IDLE peer is not establishing?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1hardmultiple choice

Open the full BGP breakdown →

Exhibit

Refer to the exhibit.

```
$ gcloud compute routers get-status router-1 --region=us-central1
kind: compute#routerStatus
result:
  bgpPeerStatus:
  - name: peer-1
    ipAddress: 169.254.1.1
    peerIpAddress: 169.254.1.2
    status: ESTABLISHED
    routesLearned: 120
  - name: peer-2
    ipAddress: 169.254.2.1
    peerIpAddress: 169.254.2.2
    status: IDLE
    routesLearned: 0
  bestRoutesForRouter:
  - dest: 10.0.0.0/8
    nextHop: 169.254.1.2
    priority: 100
  - dest: 10.0.0.0/8
    nextHop: 169.254.2.2
    priority: 200
```

A
The on-premises router is not sending routes for the IDLE peer
Why wrong: The IDLE state means BGP session is not established, not that routes are not sent.
B
The IDLE peer has a higher priority route, so it is not needed
Why wrong: Priority does not affect BGP session establishment.
C
BGP configuration mismatch between Cloud Router and on-premises router for the IDLE peer
IDLE state indicates a BGP session issue, typically misconfiguration.
D
The IDLE peer is not configured on the Cloud Router
Why wrong: The IDLE peer appears in the status, so it is configured.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

BGP configuration mismatch between Cloud Router and on-premises router for the IDLE peer

The IDLE state in BGP indicates that the session has not been established, typically due to a configuration mismatch. Since the Cloud Router shows one peer as ESTABLISHED and another as IDLE, the most likely cause is a mismatch in BGP parameters (such as AS number, peer IP, or authentication) between the Cloud Router and the on-premises router for the IDLE peer. This prevents the BGP session from transitioning out of the IDLE state.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The on-premises router is not sending routes for the IDLE peer
Why it's wrong here
The IDLE state means BGP session is not established, not that routes are not sent.
✗
The IDLE peer has a higher priority route, so it is not needed
Why it's wrong here
Priority does not affect BGP session establishment.
✓
BGP configuration mismatch between Cloud Router and on-premises router for the IDLE peer
Why this is correct
IDLE state indicates a BGP session issue, typically misconfiguration.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The IDLE peer is not configured on the Cloud Router
Why it's wrong here
The IDLE peer appears in the status, so it is configured.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Google Cloud often tests the misconception that route advertisement or route priority affects BGP session state, but the IDLE state is strictly a session establishment issue caused by misconfiguration or network reachability problems between the peers.

Detailed technical explanation

How to think about this question

BGP uses a finite state machine with states IDLE, CONNECT, ACTIVE, OPENSENT, OPENCONFIRM, and ESTABLISHED. The IDLE state is the initial state; a peer stays in IDLE if the local router cannot initiate a TCP connection (e.g., due to incorrect peer IP, wrong AS number in the remote-as statement, or mismatched BGP timers). In Google Cloud, Cloud Router BGP peers require matching AS numbers and valid peer IPs; a mismatch in the 'peer-as' or 'peer-ip' configuration will keep the session in IDLE. This is a common issue when migrating on-premises routers to a new AS or when using private AS numbers.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this PCNE question test?

Implementing hybrid interconnectivity — This question tests Implementing hybrid interconnectivity — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: BGP configuration mismatch between Cloud Router and on-premises router for the IDLE peer — The IDLE state in BGP indicates that the session has not been established, typically due to a configuration mismatch. Since the Cloud Router shows one peer as ESTABLISHED and another as IDLE, the most likely cause is a mismatch in BGP parameters (such as AS number, peer IP, or authentication) between the Cloud Router and the on-premises router for the IDLE peer. This prevents the BGP session from transitioning out of the IDLE state.

What should I do if I get this PCNE question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 30, 2026

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