How can the organization achieve this by running web server on a single instance?
It is not possible to have two IP addresses for a single instance.
The organization should create two network interfaces with the same subnet and security group to assign separate IPs to each network interface.
The organization should create two network interfaces with separate subnets so one instance can have two subnets and the respective security groups for controlled access.
The organization should launch an instance with two separate subnets using the same network interface which allows to have a separate CIDR as well as security groups.
Explanations:
It is possible for a single instance to have multiple IP addresses (primary and secondary) by using multiple network interfaces or Elastic IPs. Therefore, this option is not valid.
The organization cannot assign two separate IP addresses to the same network interface within the same subnet. Each network interface must be in its own subnet to achieve the desired security.
Creating two network interfaces with separate subnets allows the organization to manage the security separately for each interface. One interface can be internet-facing, and the other can be used for management with restricted SSH access.
A single network interface cannot span across two subnets, as each network interface must be associated with only one subnet. Thus, this option is not feasible.