A company will peer five VPCs and later connect on-prem networks over Direct Connect. What is the most important design decision up front?
A.Assign every VPC a /16 for maximum capacity
Capacity matters but /16s everywhere wastes space — and says nothing about overlap, the actual blocker.
B.Ensure all VPC and on-prem CIDRs are non-overlapping
Correct. Overlapping CIDRs make peering and hybrid routing impossible without painful NAT workarounds.
C.Use the same CIDR in each VPC and rely on NAT
Duplicate CIDRs can't be peered or routed — NAT-at-scale for overlapping networks is a documented anti-pattern.
D.Enable IPv6 only to avoid IPv4 exhaustion
IPv6 doesn't remove the need to plan; most hybrid networks still carry IPv4.
Why this answer
VPC peering, Transit Gateway, and hybrid routing all require non-overlapping CIDRs — you cannot change a VPC's primary CIDR after creation. Plan an address schema (e.g., different /16s per VPC, distinct on-prem ranges) before building.
Correct answer: B · Last reviewed 2026-10-26
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