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Implementing hybrid interconnectivity →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the Cloud Router is configured with custom advertise mode, which overrides the default behavior of automatically advertising all VPC subnet routes. When custom advertise mode is enabled, the Cloud Router only advertises the manually specified CIDR ranges to the BGP peer, so if the specific subnets like 10.1.0.0/16 are not listed in those custom ranges, they are omitted from the BGP updates—even though the broader 10.0.0.0/8 route is included. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how Cloud Router’s advertise modes interact with BGP route propagation; a common trap is assuming that custom mode still includes subnets by default. Remember the key distinction: default mode advertises all subnets automatically, while custom mode gives you full control but requires explicit inclusion of every desired prefix. A useful memory tip is “custom means curated”—if you don’t list it, it won’t be advertised.

PCNE Implementing hybrid interconnectivity Practice Question

This PCNE practice question tests your understanding of implementing hybrid interconnectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

Cloud Router configuration snippet:
```
resource "google_compute_router" "router" {
  name    = "cloud-router"
  network = "default"
  bgp {
    asn = 64512
  }
}

resource "google_compute_router_interface" "interface1" {
  name       = "if-1"
  router     = google_compute_router.router.name
  region     = "us-central1"
  ip_range   = "169.254.0.1/30"
  vpn_tunnel = google_compute_vpn_tunnel.tunnel1.self_link
}

resource "google_compute_router_peer" "peer1" {
  name                      = "peer1"
  router                    = google_compute_router.router.name
  region                    = "us-central1"
  peer_ip_address           = "169.254.0.2"
  peer_asn                  = 65001
  interface                 = "if-1"
  advertise_mode            = "CUSTOM"
  advertised_route_priority = 100
  advertised_ip_ranges {
    range = "10.0.0.0/8"
  }
}
```

Refer to the exhibit. A Cloud VPN tunnel is configured with the above Cloud Router configuration. The on-premises BGP peer is at 169.254.0.2 with ASN 65001. The on-premises router is receiving the route 10.0.0.0/8 from the Cloud Router, but it is not receiving any of the specific subnets (e.g., 10.1.0.0/16) that exist in the VPC. What is the most likely cause?

Clue words in this question

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

  • 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.

Cloud Router configuration snippet:
```
resource "google_compute_router" "router" {
  name    = "cloud-router"
  network = "default"
  bgp {
    asn = 64512
  }
}

resource "google_compute_router_interface" "interface1" {
  name       = "if-1"
  router     = google_compute_router.router.name
  region     = "us-central1"
  ip_range   = "169.254.0.1/30"
  vpn_tunnel = google_compute_vpn_tunnel.tunnel1.self_link
}

resource "google_compute_router_peer" "peer1" {
  name                      = "peer1"
  router                    = google_compute_router.router.name
  region                    = "us-central1"
  peer_ip_address           = "169.254.0.2"
  peer_asn                  = 65001
  interface                 = "if-1"
  advertise_mode            = "CUSTOM"
  advertised_route_priority = 100
  advertised_ip_ranges {
    range = "10.0.0.0/8"
  }
}
```

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

✓

The Cloud Router is configured with custom advertise mode and is only advertising the manually specified ranges.

The Cloud Router is configured with custom advertise mode, which means it only advertises the manually specified CIDR ranges to the on-premises BGP peer. Since the specific subnets (e.g., 10.1.0.0/16) are not included in the custom advertised ranges, the on-premises router receives only the explicitly listed 10.0.0.0/8 route, not the more specific subnets.

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 advertised_route_priority is set too low, causing the routes to be suppressed.

    Why it's wrong here

    Route priority does not suppress routes; it affects path selection if multiple paths exist.

  • ✓

    The Cloud Router is configured with custom advertise mode and is only advertising the manually specified ranges.

    Why this is correct

    Custom mode means only the listed ranges are advertised; VPC subnets are not included unless explicitly added.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    The BGP session is not established due to ASN mismatch.

    Why it's wrong here

    The session is up since the peer is receiving a route.

  • ✗

    The on-premises peer ASN is incorrect.

    Why it's wrong here

    The configuration matches the on-premises ASN (65001), so it's correct.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Google Cloud often tests the distinction between route advertisement control (custom vs. default mode) and route selection attributes (like priority/MED), leading candidates to incorrectly attribute missing routes to priority settings rather than advertisement configuration.

Detailed technical explanation

How to think about this question

In Google Cloud, Cloud Router supports three advertisement modes: default (advertises all VPC subnets), custom (only manually specified ranges), and no advertisement. When using custom mode, the router sends only the prefixes listed in the `--advertised-ip-ranges` parameter, even if more specific subnets exist in the VPC. This behavior is controlled by BGP UPDATE messages, where the Network Layer Reachability Information (NLRI) field contains only the explicitly configured prefixes.

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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.

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: The Cloud Router is configured with custom advertise mode and is only advertising the manually specified ranges. — The Cloud Router is configured with custom advertise mode, which means it only advertises the manually specified CIDR ranges to the on-premises BGP peer. Since the specific subnets (e.g., 10.1.0.0/16) are not included in the custom advertised ranges, the on-premises router receives only the explicitly listed 10.0.0.0/8 route, not the more specific subnets.

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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways this is tested on PCNE

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. An engineer configured a Cloud Router with the above settings. The VPC network has subnets 10.1.0.0/16 and 10.2.0.0/16, as well as subnets 10.3.0.0/16 and 10.4.0.0/16. The on-premises router is only receiving routes for 10.1.0.0/16 and 10.2.0.0/16 but not for 10.3.0.0/16 and 10.4.0.0/16. What is the cause?

easy
  • A.The BGP session is not established
  • B.The Cloud Router is in global routing mode, which does not advertise all subnets
  • ✓ C.The Cloud Router is set to custom advertisement mode, and the missing subnets are not included in the advertised IP ranges
  • D.The on-premises router has a filter that blocks the other routes

Why C: Option C is correct because when a Cloud Router is configured in custom advertisement mode, it only advertises the specific CIDR ranges explicitly listed in the 'Advertised IP ranges' field. Since the missing subnets (10.3.0.0/16 and 10.4.0.0/16) are not included in that list, they are not propagated via BGP to the on-premises router, even though they exist in the VPC.

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Last reviewed: Jun 30, 2026

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This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.