Sec. 7: AWS Fundamentals: ELB + ASG

Scaling an EC2 instance from r4.large to r4.4xlarge is called .....................

• Horizontal Scalability

• Vertical Scalability

Running an application on an Auto Scaling Group that scales the number of EC2 instances in and out is called .....................

• Vertical Scalability

• Horizontal Scalability

Elastic Load Balancers provide a .......................

• static IPv4 we can use in our application

• static DNS name we can use in our application

• static IPv6 we can use in our application

Answer explanation

Only Network Load Balancer provides both static DNS name and static IP. While, Application Load Balancer provides a static DNS name but it does NOT provide a static IP. The reason being that AWS wants your Elastic Load Balancer to be accessible using a static endpoint, even if the underlying infrastructure that AWS manages changes.

You are running a website on 10 EC2 instances fronted by an Elastic Load Balancer. Your users are complaining about the fact that the website always asks them to re-authenticate when they are moving between website pages. You are puzzled because it's working just fine on your machine and in the Dev environment with 1 EC2 instance. What could be the reason?

• The Elastic Load Balancer does not have Sticky Sessions enabled

• Your website must have an issue when hosted on multiple EC2 instances

• The EC2 instances log out users as they can't see their IP addresses, instead, they receive ELB IP addresses.

Answer explanation

ELB Sticky Session feature ensures traffic for the same client is always redirected to the same target (e.g., EC2 instance). This helps that the client does not lose his session data.

You are using an Application Load Balancer to distribute traffic to your website hosted on EC2 instances. It turns out that your website only sees traffic coming from private IPv4 addresses which are in fact your Application Load Balancer's IP addresses. What should you do to get the IP address of clients connected to your website?

• Modify your website's frontend so that users send their IP in every request

• Modify your website's backend to get the client IP address from X-Forwarded-For header

• Modify your website's backend to get the client IP address from X-Forwarded-Port header

• Modify your website's backend to get the client IP address from X-Forwarded-Proto header

Answer explanation

When using an Application Load Balancer to distribute traffic to your EC2 instances, the IP address you'll receive requests from will be the ALB's private IP addresses. To get the client's IP address, ALB adds an additional header called X-Forwarded-For contains the client's IP address.

You hosted an application on a set of EC2 instances fronted by an Elastic Load Balancer. A week later, users begin complaining that sometimes the application just doesn't work. You investigate the issue and found that some EC2 instances crash from time to time. What should you do to protect users from connecting to the EC2 instances that are crashing?

• Enable ELB Stickiness

• Enable SSL Termination

• Enable ELB Health Checks

• Enable Cross-Zone Load Balancing

Answer explanation

When you enable ELB Health Checks, your ELB won't send traffic to unhealthy (crashed) EC2 instances.

You are working as a Solutions Architect for a company and you are required to design an architecture for a high-performance, low-latency application that will receive millions of requests per second. Which type of Elastic Load Balancer should you choose?

• Application Load Balancer

• Classic Load Balancer

• Network Load Balancer

Answer explanation

Network Load Balancer provides the highest performance and lowest latency if your application needs it.

Application Load Balancers support the following protocols, EXCEPT:

• HTTP

• HTTPS

• WebSocket

• TCP

Answer explanation

Network Load Balancers support both TCP and UDP protocols.

Application Load Balancers can route traffic to different Target Groups based on the following, EXCEPT:

• Hostname

• Client's Location (Geography)

• Request URL Path

• Source IP Address

Answer explanation

ALBs can route traffic to different Target Groups based on URL Path, Hostname, HTTP Headers, and Query Strings.

Registered targets in a Target Groups for an Application Load Balancer can be one of the following, EXCEPT:

• Network Load Balancer

• Lambda Functions

• Private IP Addresses

• EC2 Instances