A user has configured a VPC with a new subnet. The user has created a security group. The user wants to
configure that instances of the same subnet communicate with each other. How can the user configure this
with the security group?

A.
There is no need for a security group modification as all the instances can communicate with each other
inside the same subnet

B.
Configure the subnet as the source in the security group and allow traffic on all the protocols and ports

C.
Configure the security group itself as the source and allow traffic on all the protocols and ports

D.
The user has to use VPC peering to configure this

Explanation:
A Virtual Private Cloud (VPC. is a virtual network dedicated to the user’s AWS account. AWS provides two
features that the user can use to increase security in VPC: security groups and network ACLs. Security groups
work at the instance level. If the user is using the default security group, it will have a rule which allows the
instances to communicate with other. For a new security group, the user has to specify the rule, add it to define
the source as the security group itself, and select all the protocols and ports for that source.