Examkin

Question

Difficulty: HardPlanning Virtual Private Cloud (VPC) Networks and Subnets

A cloud network engineering team is planning to expand an existing primary subnet CIDR block within a custom-mode Virtual Private Cloud (VPC) network to accommodate business growth. The VPC network connects to on-premises data centers via Cloud VPN and is scheduled to establish a VPC Network Peering connection with a partner organization. What is the correct sequence of steps to properly plan, validate, and execute this primary subnet range expansion without causing network outages or IP address range conflicts?

  1. 1Audit existing IP address allocations across the VPC network, hybrid Cloud VPN tunnels, and partner networks to identify unallocated, contiguous IP space.
  2. 2Calculate the target expanded CIDR range (for example, expanding from 10.10.0.0/2410.10.0.0/24 to 10.10.0.0/2310.10.0.0/23) ensuring strict adherence to bit boundary alignment and Google Cloud VPC constraints.
  3. 3Execute the Google Cloud subnet range expansion configuration change against the primary IP range of the target subnet without recreating instances or deleting the subnet.
  4. 4Update VPC firewall rules, organizational access policies, and on-premises route advertisements via Cloud Router to accommodate the expanded host IP space.

Answer

The correct procedural order is: 1) Audit existing IP address allocations across local, hybrid, and peered environments; 2) Calculate the expanded CIDR prefix complying with bit boundary alignment; 3) Execute the non-disruptive subnet expansion operation in Google Cloud; 4) Update routing advertisements and firewall rules to accommodate the new host address space.
Subnet expansion in an enterprise GCP environment requires a structured progression: first, auditing all existing and planned connected networks (hybrid VPN and VPC Peering) prevents catastrophic IP address collisions. Second, determining a bit-boundary aligned expanded mask ensures compliance with GCP subnet rules. Third, expanding the subnet in GCP is performed as a non-disruptive live configuration update. Fourth, downstream security rules and Cloud Router BGP advertisements must be updated to ensure end-to-end connectivity across the new host range.

Step-by-Step Solution

1
Perform IP allocation audit across connected environments
Identified contiguous, unallocated IP blocks and confirmed zero overlap with hybrid VPN routes or planned VPC Network Peering CIDRs.
VPC Network Peering and Cloud VPN require completely disjoint IP ranges; attempting to expand a subnet into an already allocated or advertised range breaks routing and causes peering establishment failures.
2
Define valid expanded subnet CIDR notation
Calculated a valid expanded range (e.g., 10.10.0.0/2410.10.0.0/24 expanding to 10.10.0.0/2310.10.0.0/23) that encompasses the existing base address.
Google Cloud VPC primary subnets can only be expanded to a larger prefix length (smaller mask number) without changing the network starting address, ensuring bit-boundary alignment.
3
Apply subnet expansion in Google Cloud
The primary IP range of the active subnet is updated seamlessly while running Compute Engine virtual machines maintain active connections.
GCP supports online, zero-downtime subnet CIDR expansion without deleting resources or interrupting current workload IP bindings.
4
Synchronize network security and routing policies
Cloud Routers advertise the new netmask over BGP, and VPC firewall rules permit traffic across the expanded IP space.
Expanding the subnet definition in the VPC control plane does not automatically grant external or cross-premises access unless BGP routes and firewall filters encompass the extended block.

Key Concept

VPC Subnet Expansion & Non-Overlapping IP Planning
Estimated Time:2m 0s
Rate this question

Topics

Planning Virtual Private Cloud (VPC) Networks and Subnets

More questions from this topic