- 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.