Cross-zone load balancing in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable cross-zone load balancing on the AWS Elastic Load Balancer.

AWS

resource "aws_lb" "example" {
  name               = "example-lb"
  internal           = false
  load_balancer_type = "application"
  subnets            = ["subnet-12345678", "subnet-87654321"]

  enable_cross_zone_load_balancing = [1]
}

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

C"enabled"

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using string values like "enabled" instead of boolean true.

Setting the value to false disables cross-zone load balancing.

Setting enable_cross_zone_load_balancing to true enables cross-zone load balancing on the AWS load balancer.

2fill in blank

medium

Complete the code to create a target group with cross-zone load balancing enabled on the load balancer.

AWS

resource "aws_lb_target_group" "example_tg" {
  name     = "example-tg"
  port     = 80
  protocol = "HTTP"
  vpc_id   = "vpc-12345678"

  [1] = true
}

Drag options to blanks, or click blank then click option'

Across_zone_load_balancing

Bcross_zone_balancing

Ccross_zone_lb

Denable_cross_zone_load_balancing

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect attribute names like 'cross_zone_load_balancing' or 'cross_zone_lb'.

Misspelling the attribute name.

The correct attribute to enable cross-zone load balancing on the target group is enable_cross_zone_load_balancing.

3fill in blank

hard

Fix the error in the code to correctly enable cross-zone load balancing for the AWS Classic Load Balancer.

AWS

resource "aws_elb" "example" {
  name               = "example-classic-lb"
  availability_zones = ["us-west-2a", "us-west-2b"]

  [1] = true
}

Drag options to blanks, or click blank then click option'

Across_zone_lb_enabled

Bcross_zone_load_balancing

Cenable_cross_zone_load_balancing

Dcross_zone_balancing

Attempts:

3 left

💡 Hint

Common Mistakes

Using enable_cross_zone_load_balancing which is for ALB/NLB.

Misspelling the attribute name.

For AWS Classic Load Balancer, the attribute to enable cross-zone load balancing is cross_zone_load_balancing.

4fill in blank

hard

Fill both blanks to configure an Application Load Balancer with cross-zone load balancing enabled and access logs turned on.

AWS

resource "aws_lb" "example" {
  name               = "example-alb"
  load_balancer_type = "application"
  subnets            = ["subnet-11111111", "subnet-22222222"]

  [1] = true

  access_logs {
    [2] = "my-log-bucket"
  }
}

Drag options to blanks, or click blank then click option'

Aenable_cross_zone_load_balancing

Bbucket

Caccess_log_bucket

Denable_access_logs

Attempts:

3 left

💡 Hint

Common Mistakes

Using access_log_bucket instead of bucket inside access_logs.

Trying to enable access logs with a boolean attribute instead of setting the bucket.

To enable cross-zone load balancing, use enable_cross_zone_load_balancing. For access logs, the bucket name is set with bucket inside the access_logs block.

5fill in blank

hard

Fill all three blanks to create a Network Load Balancer with cross-zone load balancing enabled, health check configured, and a target group attached.

AWS

resource "aws_lb" "nlb" {
  name               = "example-nlb"
  load_balancer_type = "network"
  subnets            = ["subnet-aaaaaaa", "subnet-bbbbbbb"]

  [1] = true
}

resource "aws_lb_target_group" "tg" {
  name     = "example-tg"
  port     = 80
  protocol = "TCP"
  vpc_id   = "vpc-abcdef12"

  health_check {
    [2] = "/"
    [3] = 30
  }
}

Drag options to blanks, or click blank then click option'

Aenable_cross_zone_load_balancing

Bpath

Cinterval

Dcross_zone_load_balancing

Attempts:

3 left

💡 Hint

Common Mistakes

Using cross_zone_load_balancing for NLB instead of enable_cross_zone_load_balancing.

Confusing health check attributes names.

For Network Load Balancer, cross-zone load balancing is enabled with enable_cross_zone_load_balancing. Health check path and interval configure the check URL and frequency.

Practice

1. What is the main benefit of enabling cross-zone load balancing in AWS Elastic Load Balancer?

easy

A. It increases the maximum number of connections per target.

B. It automatically scales the number of Availability Zones.

C. It evenly distributes incoming traffic across all registered targets in all enabled Availability Zones.

D. It encrypts all traffic between the load balancer and targets.

Solution

1. Step 1: Understand cross-zone load balancing purpose

   Cross-zone load balancing spreads traffic evenly across targets in all zones, preventing uneven load.

2. Step 2: Compare options to this purpose

   Only It evenly distributes incoming traffic across all registered targets in all enabled Availability Zones. describes this even distribution. Other options describe unrelated features.

3. Final Answer:

   It evenly distributes incoming traffic across all registered targets in all enabled Availability Zones. -> Option C

4. Quick Check:

   Cross-zone load balancing = even traffic spread [OK]

Hint: Cross-zone means traffic spreads evenly across zones [OK]

Common Mistakes:

• Confusing cross-zone with encryption or scaling
• Thinking it increases max connections per target
• Assuming it changes number of zones automatically

2. Which of the following is the correct way to enable cross-zone load balancing in an AWS Application Load Balancer using Terraform?

easy

A. enable_cross_zone_load_balancing = false

B. cross_zone_load_balancing = true

C. cross_zone_enabled = true

D. enable_cross_zone_load_balancing = true

Solution

1. Step 1: Recall Terraform attribute for cross-zone load balancing

   The correct attribute is enable_cross_zone_load_balancing and it must be set to true to enable.

2. Step 2: Match options to correct syntax

   Only enable_cross_zone_load_balancing = true uses the exact attribute name and sets it to true.

3. Final Answer:

   enable_cross_zone_load_balancing = true -> Option D

4. Quick Check:

   Terraform attribute = enable_cross_zone_load_balancing true [OK]

Hint: Look for exact attribute name with true value [OK]

Common Mistakes:

• Using incorrect attribute names like cross_zone_load_balancing
• Setting the value to false instead of true
• Confusing with other unrelated settings

3. Given the following AWS CLI command to enable cross-zone load balancing on a Classic Load Balancer:

aws elb modify-load-balancer-attributes --load-balancer-name my-load-balancer --load-balancer-attributes '{"CrossZoneLoadBalancing":{"Enabled":true}}'

What will be the effect of running this command?

medium

A. Cross-zone load balancing will be disabled for the load balancer.

B. Cross-zone load balancing will be enabled, distributing traffic evenly across zones.

C. The load balancer will be deleted.

D. The command will fail due to syntax error.

Solution

1. Step 1: Analyze the AWS CLI command structure

   The command modifies load balancer attributes, specifically enabling CrossZoneLoadBalancing by setting Enabled to true.

2. Step 2: Understand the effect of enabling CrossZoneLoadBalancing

   Enabling it causes traffic to be evenly distributed across all registered targets in all zones.

3. Final Answer:

   Cross-zone load balancing will be enabled, distributing traffic evenly across zones. -> Option B

4. Quick Check:

   Enable CrossZoneLoadBalancing true = even traffic spread [OK]

Hint: Enabled true means cross-zone load balancing is active [OK]

Common Mistakes:

• Thinking the command disables the feature
• Assuming the load balancer is deleted
• Believing the command syntax is incorrect

4. You configured cross-zone load balancing on your Network Load Balancer but notice traffic is still uneven across zones. What is the most likely cause?

medium

A. You forgot to register targets in all Availability Zones.

B. Cross-zone load balancing is not supported on Network Load Balancers.

C. Cross-zone load balancing requires manual DNS updates.

D. You must enable cross-zone load balancing on each target instance.

Solution

1. Step 1: Recall cross-zone load balancing support on Network Load Balancers

   Network Load Balancers support cross-zone load balancing, but it must be enabled and targets must be registered in all zones.

2. Step 2: Identify why traffic is uneven

   If targets are missing in some zones, traffic cannot be balanced evenly despite cross-zone load balancing being enabled.

3. Final Answer:

   You forgot to register targets in all Availability Zones. -> Option A

4. Quick Check:

   Targets missing in zones = uneven traffic [OK]

Hint: Ensure targets exist in all zones for balancing [OK]

Common Mistakes:

• Thinking cross-zone load balancing is unsupported on NLB
• Believing DNS updates are needed
• Assuming enabling on targets is required

5. You have an Application Load Balancer spanning three Availability Zones with cross-zone load balancing enabled. One zone has only one healthy target, while the others have three each. How does cross-zone load balancing affect traffic distribution?

hard

A. Traffic is evenly distributed across all targets regardless of zone count.

B. Traffic is evenly distributed across zones, so the zone with one target gets one-third of traffic.

C. Traffic is sent only to zones with the most targets.

D. Traffic is distributed randomly without considering zones or targets.

Solution

1. Step 1: Understand cross-zone load balancing behavior

   With cross-zone load balancing enabled, each load balancer node distributes traffic evenly across all healthy registered targets, regardless of their Availability Zone.

2. Step 2: Apply to given scenario

   Total healthy targets: 1 + 3 + 3 = 7. Each target receives approximately equal traffic (1/7), so the zone with one target gets about 1/7 of total traffic.

3. Final Answer:

   Traffic is evenly distributed across all targets regardless of zone count. -> Option A

4. Quick Check:

   Cross-zone load balancing = even across all targets [OK]

Hint: Cross-zone balances evenly across all targets, ignoring zone boundaries [OK]

Common Mistakes:

• Confusing with default zone-isolated balancing (even per zone)
• Thinking traffic prefers zones with more targets
• Believing distribution ignores target count