A company allocates CIDRs independently in 200 accounts and repeatedly discovers overlaps during network mergers. Which approach best prevents recurrence?

1. Use the same /16 for all VPCs because separate accounts guarantee routing uniqueness.
2. Use VPC IPAM pools with organizational allocation rules and monitored address usage.
3. Create a Route 53 record for each CIDR to eliminate overlapping addresses.
4. Continue manual allocation and resolve conflicts only after every deployment.