[AWS] VPC – Subnets and Routing Tables

Subnets

  • A subnet is an isolated local network confined in a single AZ.
  • Different application tiers are in different subnets.
  • 5 IPs are reserved for a subnet (ex. /24 network  251 IPs available)
    • 0 (first) – Network, 1 – Router, 2 – DNS, 3 – Future, X (last) – Broadcast
  • Subnets must be associated with a route table.
  • Subnets are by default private unless created in a default VPC.
  • The CIDR block of a subnet cannot overlap the CIDR blocks of other subnets in the same VPC.
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