Subnets

A smaller network of a larger network or it can also be defined as division of a larger network into multiple sub networks separated by subnet mask.

It can also be said that division of a logical IP address into sub network.

Subnet mask

It is a 32 bit number that defines the range of IP addresses that can be used within a network or subnet.

• Divided into Network Bit (1) and Host Bit (0)
• Subnetting is process of creating a sub network within a network.
• Subnetting can be performed either by using Fixed Length Subnet Mask (FLSM) or Variable Length Subnet Mask (VLSM)
• In Fixed Length Subnet Mask (FLSM) All subnetwork within the same network use the same subnet mask.
• In Variable Length Subnet Mask (VLSM) Some networks within the same network can use different subnet mask.
• CIDR is similar to subnetting but works with classless IP address or VLSM

Types of Subnet in VPC

There are two types of VPC -

Private Subnets

• It was submitted doesn't have a route to the Internet gateway the summit is known as private subnet.
• When you create a VPC you must specify an IPv4 CIDR block for the VPC.

Public Subnets

• It was subnet traffic is routed to an Internet gateway, the subnet is known as public subnet.
• If you want your distance in a public subnet to communicate with the Internet over IPv4 it must be a public IPv4 elastic IP address.

Points to remember

• Only allowed block size is /16 to /28
• There are five IP addresses that is reserved by AWS and it cannot be assigned or used in a VPC. Those addresses are -

AWS doesn't support broadcast in a VPC but reserve the address