Question

How many IP addresses are reserved in each VPC subnet?

Answer 1

In each VPC subnet, the first four and the last one IP addresses are reserved for internal networking purposes, meaning they are not available for general use.

Step-by-step explanation:

Reserved IP Addresses in VPC Subnets

When dealing with Virtual Private Cloud (VPC) subnets, certain IP addresses are reserved for specific purposes and therefore are not available for use with general devices. Each subnet in a VPC will reserve the first four and the last one IP addresses for internal networking purposes. To illustrate, in a subnet with a CIDR block of 10.0.1.0/24, the IP addresses 10.0.1.0 (network address), 10.0.1.1 (VPC router), 10.0.1.2 (DNS services), 10.0.1.3 (future use), and 10.0.1.255 (network broadcast) are reserved. It is crucial for network administrators and system architects designing a VPC to take this into account to ensure adequate IP address availability for their resources.

Answer 2

In each subnet of an AWS VPC, five IP addresses are reserved for AWS internal networking purposes and are not available for general use. These include the network address, VPC router, DNS services, future use, and network broadcast address.

Step-by-step explanation:

In the context of Amazon Web Services (AWS), a Virtual Private Cloud (VPC) is an isolated network within the AWS Cloud. When you create a subnet within a VPC, AWS reserves five IP addresses within every subnet's address range. These reserved IP addresses are not available for use by EC2 instances or other services.

The first four IP addresses and the last one in each subnet CIDR block are reserved by AWS for internal networking purposes. For example, the first address (.0) is the network address, the second (.1) is reserved for the VPC router, the third (.2) is reserved for DNS services, the fourth (.3) is reserved for future use, and the last address is reserved as the network broadcast address. These addresses cannot be used for standard instances or applications.

To sum up, in a VPC subnet, AWS reserves a total of five IP addresses that are used for network management and cannot be assigned to user resources.