PCNE Configuring Network Services Practice Question
Exhibit
Refer to the exhibit. $ gcloud compute routers describe router-us bgp: advertiseMode: CUSTOM advertisedGroups: - ALL_SUBNETS advertisedIpRanges: - range: 10.1.0.0/24 - range: 10.2.0.0/24 asn: 65000 keepaliveInterval: 20 bgpPeers: - interfaceName: if-bgp ipAddress: 169.254.1.1 peerIpAddress: 169.254.1.2 peerAsn: 65001 advertisedRoutePriority: 100
Refer to the exhibit. The Cloud Router is configured with custom BGP advertisements. The on-premises router receives only the two advertised ranges (10.1.0.0/24 and 10.2.0.0/24) but not the VPC subnets (e.g., 10.3.0.0/24). What is the most likely reason?
⚠ Common exam trap
Google Cloud often tests the misconception that Cloud Router's custom advertisement configuration automatically overrides on-premises filtering, when in reality BGP attributes like communities and AS-path are the primary mechanisms for route filtering on the receiving side.
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 on-premises router is filtering routes based on the BGP community or AS path.
Cloud Router custom advertisements can include BGP communities or AS-path attributes that the on-premises router may be filtering. If the on-premises router is configured to reject routes based on these attributes (e.g., only accepting routes with a specific community or AS-path length), it would drop the VPC subnet routes even if they are advertised. The scenario states that only the two explicitly advertised ranges are received, indicating a filtering mechanism on the on-premises side rather than a Cloud Router misconfiguration.
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 configured to accept only prefixes longer than /24.
Why it's wrong here
The VPC subnet is /24 as well, so it should be accepted.
- ✗
The advertised route priority of 100 is too high, causing the routes to be ignored.
Why it's wrong here
Priority doesn't affect advertisement.
- ✗
The Cloud Router's custom advertisement includes both the ALL_SUBNETS group and the explicit ranges, so all subnets should be advertised.
Why it's wrong here
The configuration seems correct; the issue is likely on the on-premises side.
- ✓
The on-premises router is filtering routes based on the BGP community or AS path.
Why this is correct
On-premises routers often have ingress filters that can drop routes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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