As part of my preparation for the AWS SysOps Administrator certification exam, I recently studied the “Amazon Web Services (AWS) Fundamentals for System Administrators” course on Pluralsight. Below, I’ve distilled my key takeaways and observations regarding AWS networking, particularly focusing on Virtual Private Clouds (VPCs), which are essential for any AWS system administrator or cloud architect.

What is a VPC?

A Virtual Private Cloud (VPC) is a logically isolated network within the AWS cloud. Every AWS subscription comes with a root VPC, and you can further segment it into smaller VPCs as needed. VPCs are free, but setting up VPN connections for secure access to on-premises resources incurs additional costs.

AWS organizes services into layers within the VPC reference model:

  1. Global Infrastructure (AWS-managed services)
  2. Networking (where VPCs reside)
  3. Compute, Storage, Database (customer-managed environments)
  4. Application Services (AWS-managed services)
  5. Deployment & Automation (AWS-managed services)

VPC Architecture & Characteristics

VPCs are region-specific, and within a region, they span multiple Availability Zones. Each VPC is further subdivided into subnets, and AWS provides a built-in router to connect these subnets. AWS supports CIDR blocks from /16 to /28 for assigning IP address ranges to VPCs.

When creating a VPC, AWS offers the option to set hardware tenancy for dedicated network hardware, though this comes with higher costs. Tagging resources is recommended to ensure clear identification and management.

VPC Access Methods

There are several ways to access VPC resources:

  • Internet Gateway (IGW): Provides ingress and egress for instances within a VPC.
  • Virtual Private Gateway (VPG): AWS’s side of a secure VPN connection.
  • Customer Gateway (CG): The customer-managed side of a VPN connection, typically using on-premises hardware.

Alternatively, Direct Connect offers a dedicated, isolated connection to your VPC, bypassing the internet to provide high-availability and low-latency connectivity.

VPC Security

Security within VPCs is enforced through Security Groups and Access Control Lists (ACLs):

  • Security Groups function as resource-level firewalls, controlling both inbound and outbound traffic. They are stateful, meaning that return traffic is automatically allowed when outbound traffic is permitted.
  • ACLs are subnet-level firewalls that enforce stateless traffic filtering, requiring explicit rules for both inbound and outbound traffic.

Configuring a VPC

When setting up a VPC, several critical components come into play:

  • AWS automatically creates an Internet Gateway by default. Assigning elastic IP addresses to instances within a VPC makes them externally accessible.
  • Key VPN components include the Customer Gateway (customer side) and the Virtual Private Gateway (AWS side). VPN connections can be managed and viewed in the AWS console.
  • Network ACLs define inbound and outbound rules and can be associated with multiple subnets.
  • Security Groups apply security rules to all instances within the group, controlling access based on protocol, port, and source IP.

Instances can also be configured to:

  • Automatically join a Windows domain.
  • Specify IAM roles for access control.
  • Protect against accidental termination by configuring settings that prevent deletion via API or management console.
  • Enable CloudWatch monitoring for tracking resource performance.

VPC Peering

VPC peering allows you to connect multiple VPCs, but note that no transitive peering is allowed. This means that if VPC1 is connected to both VPC2 and VPC3, VPC2 and VPC3 cannot communicate unless you explicitly establish a separate connection. Additionally, VPCs cannot have overlapping IP address ranges (e.g., VPC1 cannot use the same CIDR block as VPC2).

In-depth VPC Configuration

The course also covered more advanced VPC configuration topics. Some highlights include:

  • Region switching: AWS allows you to switch between regions easily using a drop-down menu in the console.
  • Non-default tenancy: Dedicated hardware tenancy can be selected for enhanced security and performance.
  • Core components for internet access: A VPC, subnets, and an internet gateway are the basic building blocks for enabling internet access.
  • Routing tables are automatically set up to allow communication between subnets when they are created.
  • When creating an Internet Gateway, you need to attach it to a VPC to enable internet connectivity.

Final Thoughts

As I continue my journey towards earning the AWS SysOps Administrator certification, the AWS VPC concepts and networking tools are becoming more essential to understanding how AWS handles cloud infrastructure. The ability to segment, secure, and scale VPCs is a powerful feature of AWS, and mastering these capabilities will not only help me in my certification exam but also in real-world cloud architecture scenarios.

AWS provides robust management and security features for VPCs, but understanding the fundamentals—like security groups, ACLs, and VPC peering—is critical for efficient administration. Whether configuring secure VPNs or managing complex multi-subnet architectures, understanding AWS networking will empower you to design and manage scalable, secure environments in the cloud.