How overlaps happen
Cloud consoles suggest default address ranges, and teams in different departments or acquired companies often accept them. When those networks need to connect, identical ranges cannot be routed directly.
Prevention: an address plan
Before connecting clouds, create an address plan that gives each environment, region and account a unique range. Leave room to grow.
Track allocations
Use an IP address management tool or a simple shared registry so every new network draws from the plan.
When overlaps already exist
- Renumber the smaller or newer environment if practical.
- NAT at the boundary — translate one side to a unique range. NAT Gateway services can do this centrally.
- Expose services, not networks — use private service endpoints or proxies for the few things that need to cross.
Routing hygiene
Advertise only the prefixes that need to be reachable, and filter what you accept. A cloud router on the fabric can enforce this centrally.
Getting addressing right early saves months of work later.
