Update dev VPC CIDR to 10.1.0.0/16 #8
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- Change VPC CIDR from 10.0.0.0/16 to 10.1.0.0/16 - Reorganizing network allocations for better segmentation
WalkthroughA single Terragrunt configuration file was updated to change the VPC CIDR block allocation for the dev environment from 10.0.0.0/16 to 10.1.0.0/16. This is a straightforward parameter modification with no architectural or control flow changes. Changes
Estimated code review effort🎯 1 (Trivial) | ⏱️ ~2 minutes Poem
Pre-merge checks and finishing touches✅ Passed checks (3 passed)
✨ Finishing touches🧪 Generate unit tests (beta)
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📒 Files selected for processing (1)
dev/vpc/terragrunt.hcl(1 hunks)
🧰 Additional context used
🔍 Remote MCP Exa, Notion
Summary
Based on my comprehensive search across Linear, Notion, and Exa, I have found critical information that conflicts with this PR:
⚠️ Conflict Detected: CIDR Allocation Mismatch
The PR aims to change the dev VPC CIDR from 10.0.0.0/16 to 10.1.0.0/16. However, according to the Network CIDR Allocation Table in Notion, there is a significant conflict:
Current Allocation (per Notion):
- Development:
10.0.0.0/16(Active - Primary dev workloads) - Production:
10.1.0.0/16(Active - Production services) - Staging:
10.2.0.0/16(Reserved) - DR:
10.3.0.0/16(Reserved)
The Problem: The PR is attempting to assign 10.1.0.0/16 (currently allocated to Production) to the Development environment. This creates a direct routing conflict with active production infrastructure.
Additional Concerns (from Notion documentation)
The Network CIDR Allocation Table explicitly warns:
⚠️ Do not modify CIDR allocations without Network Engineering approval. Changing a VPC's CIDR range requires:
- VPC peering updates
- Route table modifications
- Security group rule updates
- Transit Gateway attachment changes
- DNS resolver rule updates
Terragrunt Configuration Best Practices
The search results confirm that VPC CIDR changes are significant infrastructure modifications with multiple downstream dependencies.
Recommendation
Do NOT approve this PR in its current form. This change conflicts with the documented Production CIDR allocation. Before proceeding:
- Verify Network Engineering approval is documented
- Confirm which environment actually needs the IP reallocation
- Ensure all dependent resources (VPC peering, route tables, security groups, Transit Gateway, DNS) have been identified and updated
- Consider using an unallocated range (e.g.,
10.4.0.0/16or higher) to avoid conflicts
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| inputs = { | ||
| vpc_cidr = "10.0.0.0/16" | ||
| vpc_cidr = "10.1.0.0/16" |
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🧩 Analysis chain
🏁 Script executed:
# First, check if the file exists and read its content
ls -la dev/vpc/terragrunt.hcl 2>/dev/null || echo "File not found"Repository: coderabbitai/rabbits-playground
Length of output: 145
🏁 Script executed:
# Search for CIDR allocation references in the codebase
rg "10\.[0-3]\.0\.0/16" --type hcl --type tf --type json -A 2 -B 2Repository: coderabbitai/rabbits-playground
Length of output: 102
🏁 Script executed:
# Look for network configuration or CIDR documentation
find . -type f \( -name "*network*" -o -name "*cidr*" -o -name "*allocation*" \) -iname "*.md" -o -iname "*.txt" -o -iname "*.yaml" | head -20Repository: coderabbitai/rabbits-playground
Length of output: 57
🏁 Script executed:
# Search for references to Production and Development VPC CIDR in configuration files
rg -i "(production|development|prod|dev).*cidr|vpc.*10\." --type hcl --type tf --type yaml -B 2 -A 2Repository: coderabbitai/rabbits-playground
Length of output: 102
🏁 Script executed:
# Look for VPC peering, route tables, and security group rules that might be affected
rg -i "(vpc_peering|route_table|security_group|transit.*gateway)" --type hcl --type tf | head -30Repository: coderabbitai/rabbits-playground
Length of output: 102
🏁 Script executed:
# Read the actual file content
cat -n dev/vpc/terragrunt.hclRepository: coderabbitai/rabbits-playground
Length of output: 512
🏁 Script executed:
# Search for CIDR patterns across all files without file type filtering
rg "10\.[0-3]\.0\.0/16" -B 2 -A 2Repository: coderabbitai/rabbits-playground
Length of output: 834
🏁 Script executed:
# Search for any references to production/development CIDR across the codebase
rg "(vpc_cidr|CIDR|cidr)" -i --type-list | head
rg "(vpc_cidr|CIDR|cidr)" -i -B 1 -A 1Repository: coderabbitai/rabbits-playground
Length of output: 3740
🏁 Script executed:
# Look for documentation files that might contain CIDR allocations
find . -type f \( -name "*.md" -o -name "*.txt" -o -name "*.rst" \) | xargs grep -l -i "cidr\|network\|allocation" 2>/dev/null | head -10Repository: coderabbitai/rabbits-playground
Length of output: 86
🔍 Additional research query:
Search Notion for network CIDR allocation table and network engineering requirements for VPC changes. Look for documentation about production and development CIDR ranges (10.0.0.0/16, 10.1.0.0/16, 10.2.0.0/16, 10.3.0.0/16).
💡 Result:
Network CIDR Allocation Documentation
I found the comprehensive Network CIDR Allocation Table in Notion with detailed information about your VPC network configuration:
VPC CIDR Assignments
The document defines IP address allocation for all VPCs in AWS infrastructure, coordinated with on-premises network teams to prevent routing conflicts.
CIDR Range Allocations:
- Development: 10.0.0.0/16 (Active - Primary dev workloads)
- Production: 10.1.0.0/16 (Active - Production services)
- Staging: 10.2.0.0/16 (Reserved - Future staging environment)
- DR: 10.3.0.0/16 (Reserved - Disaster recovery site)
Subnet Architecture Within VPCs
Each /16 VPC is subdivided with:
- 10.x.0.0/20, 10.x.16.0/20, 10.x.32.0/20 - Public subnets (AZ-a, AZ-b, AZ-c)
- 10.x.128.0/20, 10.x.144.0/20, 10.x.160.0/20 - Private subnets (AZ-a, AZ-b, AZ-c)
VPC Change Requirements & Network Engineering Approval Process
- VPC peering updates
- Route table modifications
- Security group rule updates
- Transit Gateway attachment changes
- DNS resolver rule updates
Network Integration Context
The corporate network uses 172.16.0.0/12, and the 10.x.0.0/8 ranges are specifically allocated for AWS to avoid overlap with corporate offices (172.16.0.0/16), data centers (172.17.0.0/16), and VPN clients (172.18.0.0/16).
Contact: [email protected] for CIDR allocation requests.,
CRITICAL: CIDR conflict with Production - DO NOT MERGE.
Both dev/vpc/terragrunt.hcl and prod/vpc/terragrunt.hcl are assigned 10.1.0.0/16. According to the Network CIDR Allocation Table, development should use 10.0.0.0/16 and production should use 10.1.0.0/16. This creates a direct routing conflict.
Update vpc_cidr to the correct development range 10.0.0.0/16 on line 14. CIDR changes require Network Engineering approval and updates to VPC peering, route tables, security groups, Transit Gateway attachments, and DNS resolver rules.
🤖 Prompt for AI Agents
In dev/vpc/terragrunt.hcl around line 14, the vpc_cidr is incorrectly set to
10.1.0.0/16 which conflicts with prod; change it to the correct dev CIDR
10.0.0.0/16 on line 14, then submit the CIDR change to Network Engineering for
approval and coordinate updates to VPC peering, route tables, security groups,
Transit Gateway attachments, and DNS resolver rules as required.
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