12 ‐ Scenario‐Based Questions for Load Balancer & Firewall in Azure and AWS - SanjeevOCI/Study GitHub Wiki

Scenario-Based Questions and Answers for Load Balancer & Firewall in Azure and AWS

Load Balancer Scenarios

1. Scenario: Configuring a Load Balancer for High Availability

Question:
You have deployed a web application across multiple availability zones. How would you configure a Load Balancer in Azure and AWS to ensure high availability?

Answer:

  • Azure:

    • Use an Azure Load Balancer (Standard SKU) for regional high availability.
    • Add VMs from multiple availability zones to the Backend Pool.
    • Configure Health Probes to monitor the availability of backend VMs.
    • Use Zone Redundant Load Balancer for resilience.

  • AWS:

    • Use an Application Load Balancer (ALB) for HTTP/HTTPS traffic.
    • Add EC2 instances from multiple availability zones to the Target Group.
    • Configure Health Checks to monitor the health of backend instances.
    • Enable Cross-Zone Load Balancing for even traffic distribution.

2. Scenario: Securing Traffic to a Load Balancer

Question:
How would you secure traffic to a Load Balancer in Azure and AWS to ensure only HTTPS traffic is allowed?

Answer:

  • Azure:

    • Configure an HTTPS Listener on the Azure Load Balancer.
    • Upload an SSL certificate to the Load Balancer.
    • Use NSG (Network Security Group) to allow only port 443 traffic to the Load Balancer.

  • AWS:

    • Configure an HTTPS Listener on the Application Load Balancer.
    • Upload an SSL certificate to the ALB using AWS Certificate Manager (ACM).
    • Use Security Groups to allow only port 443 traffic to the ALB.

3. Scenario: Load Balancer for Internal Applications

Question:
You need to set up a Load Balancer for an internal application that should not be accessible from the internet. How would you configure it in Azure and AWS?

Answer:

  • Azure:

    • Deploy an Internal Load Balancer in a private subnet.
    • Ensure the backend VMs are also in private subnets.
    • Use NSGs to restrict access to specific IP ranges or VNets.

  • AWS:

    • Deploy an Internal Application Load Balancer in private subnets.
    • Ensure the backend EC2 instances are in private subnets.
    • Use Security Groups to restrict access to specific IP ranges or VPCs.

4. Scenario: Load Balancer Health Check Failing

Question:
Your Load Balancer health check is failing for one of the backend instances. How would you troubleshoot this issue in Azure and AWS?

Answer:

  • Azure:

    • Verify the Health Probe configuration (protocol, port, and path).
    • Ensure the NSG allows traffic from the Load Balancer's IP range to the backend VM.
    • Check the application logs on the backend VM for errors.

  • AWS:

    • Verify the Health Check configuration (protocol, port, and path) in the Target Group.
    • Ensure the Security Group allows traffic from the ALB to the backend EC2 instance.
    • Check the application logs on the EC2 instance for errors.

5. Scenario: Load Balancer Scaling

Question:
Your application traffic has increased significantly, and the Load Balancer is struggling to handle the load. How would you scale the Load Balancer in Azure and AWS?

Answer:

  • Azure:

    • Use an Azure Standard Load Balancer, which automatically scales based on traffic.
    • Ensure the backend pool has sufficient VMs with Auto-Scaling enabled.

  • AWS:

    • Use an Application Load Balancer, which automatically scales to handle increased traffic.
    • Add more EC2 instances to the Target Group using Auto Scaling Groups.

Firewall Scenarios

1. Scenario: Restricting Access to a Compute Instance

Question:
You need to restrict SSH access to a compute instance to a specific IP address. How would you configure this in Azure and AWS?

Answer:

  • Azure:

    • Use a Network Security Group (NSG) to allow inbound traffic on port 22 only from the specific IP address.
    • Example NSG Rule:
      • Source: <specific-IP>/32
      • Protocol: TCP
      • Port Range: 22

  • AWS:

    • Use a Security Group to allow inbound traffic on port 22 only from the specific IP address.
    • Example Security Group Rule:
      • Source: <specific-IP>/32
      • Protocol: TCP
      • Port Range: 22

2. Scenario: Allowing Internet Access for a Private Subnet

Question:
You have a private subnet, and the instances in it need to access the internet for updates. How would you configure this securely in Azure and AWS?

Answer:

  • Azure:

    • Deploy a NAT Gateway in the VNet.
    • Associate the NAT Gateway with the private subnet.
    • Update the Route Table to route all outbound traffic (0.0.0.0/0) through the NAT Gateway.

  • AWS:

    • Deploy a NAT Gateway in a public subnet.
    • Update the Route Table for the private subnet to route all outbound traffic (0.0.0.0/0) through the NAT Gateway.

3. Scenario: Blocking Traffic from a Specific IP Range

Question:
How would you block traffic from a specific IP range to your application hosted in Azure and AWS?

Answer:

  • Azure:

    • Use an NSG to create an inbound rule to deny traffic from the specific IP range.
    • Example NSG Rule:
      • Source: <blocked-IP-range>
      • Action: Deny
      • Protocol: All

  • AWS:

    • Use a Security Group to deny traffic from the specific IP range.
    • Alternatively, use a Network ACL to block traffic from the IP range.

4. Scenario: Configuring Stateful vs Stateless Rules

Question:
What is the difference between stateful and stateless rules in Azure and AWS firewalls, and when would you use each?

Answer:

  • Azure:

    • NSGs are stateful, meaning return traffic is automatically allowed for an allowed connection.
    • Use NSGs for most scenarios where bidirectional communication is required.

  • AWS:

    • Security Groups are stateful, while Network ACLs are stateless.
    • Use Security Groups for instance-level control and Network ACLs for subnet-level control.

5. Scenario: Securing Object Storage Access

Question:
You need to allow a compute instance in a private subnet to access an Object Storage bucket securely. How would you configure this in Azure and AWS?

Answer:

  • Azure:

    • Use a Service Endpoint or Private Endpoint to enable private access to the storage account.
    • Update the Storage Account Firewall to allow traffic only from the VNet.

  • AWS:

    • Use a VPC Endpoint to enable private access to the S3 bucket.
    • Update the S3 bucket policy to allow access only from the VPC.

Summary

These scenario-based questions and answers cover practical use cases for Load Balancers and Firewalls in Azure and AWS, focusing on security, scalability, and troubleshooting.