An organization operates a custom-mode Virtual Private Cloud (VPC) in Google Cloud. A network engineer is tasked with expanding the primary IP range of `subnet-east` to accommodate additional compute instances.
The current VPC subnet allocation and connected routes are configured as follows:
- `subnet-east` primary IP range: ()
- `subnet-west` primary IP range: ()
- `subnet-central` primary IP range: ()
- On-premises network (via Cloud VPN): ()
The engineer plans to expand `subnet-east` to a prefix length to double its IP capacity. Which statement accurately describes the outcome and requirements for this expansion?
- The expansion will fail because the only valid CIDR block containing is , which overlaps with `subnet-west` ().Answer
- BThe expansion will succeed if `subnet-east` is expanded to , utilizing the unused IP addresses between `subnet-central` and `subnet-east`.
- CThe expansion will succeed if `subnet-east` is expanded to , because Google Cloud automatically re-aggregates adjacent subnets within the same VPC.
- DThe expansion will fail because Google Cloud subnets can only be expanded if the original prefix length is or smaller.
Answer
The expansion will fail because the only valid CIDR block containing is , which overlaps with `subnet-west` ().
Expanding a primary subnet IP range in a GCP Virtual Private Cloud requires two fundamental conditions: the new netmask must be smaller (broader), and the new CIDR block must encompass the existing IP range while remaining aligned on a valid binary CIDR boundary. For , the only encompassing block is (). Because is already assigned to `subnet-west`, the expanded block creates an IP overlap, causing Google Cloud to reject the expansion.
Step-by-Step Solution
Key Concept
VPC Primary Subnet Expansion CIDR Boundary and Overlap Rules
Estimated Time:2m 0s