Q: You need two VPCs in different AWS accounts to communicate privately. How do you set this up?
Option 1: VPC Peering
#AWS #Networking & VPC #L2 #Cloud #Infrastructure #VPC
🎙️ Candidate Opening & Architectural Context
""In a previous role, our monitoring paged me for a similar incident across our AWS VPC infrastructure. When addressing this question, I walk the interviewer through our production incident runbook: isolating the blast radius, checking diagnostic logs and metrics, and applying a safe fix.""
Advertisement
🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
Option 1: VPC Peering
- Create a peering connection between the two VPCs (cross-account supported).
- Accept the peering request in the other account.
- Update route tables in both VPCs to point to each other's CIDR via the peering connection.
- Update Security Groups to allow traffic from the other VPC's CIDR.
- Central hub. Connect all VPCs (and on-prem) to TGW.
- Fully transitive. Any connected VPC can reach any other.
2️⃣
Remediation & Permanent Safeguards
Limitation: Not transitive. If VPC A peers with B, and B peers with C, A can't talk to C through B. Option 2: AWS Transit Gateway Option 3: AWS PrivateLink
- Better for many VPCs. Costs more than peering.
- Expose a specific service (not the whole VPC) across accounts.
- The consumer VPC creates an Interface Endpoint pointing to the provider's endpoint service.
- Traffic stays on AWS backbone.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Create a peering connection between the two VPCs (cross-account supported).."
⚡ 60-Second Elevator Pitch Talking Points
- Create a peering connection between the two VPCs (cross-account supported).
- Accept the peering request in the other account.
- Update route tables in both VPCs to point to each other's CIDR via the peering connection.
Advertisement