Backend pools and health probes in Azure - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

How does a health probe affect backend pool traffic?

In Azure Load Balancer, what happens when a backend pool VM fails the health probe?

A The VM is restarted automatically by the load balancer.

B The VM continues to receive traffic but logs an error.

C The VM is removed from the backend pool and stops receiving new traffic.

D The load balancer redirects traffic to the failing VM to test recovery.

💡 Hint

Think about how the load balancer ensures only healthy VMs get traffic.

The health probe checks VM health. If a VM fails, it is removed from the backend pool to avoid sending traffic to an unhealthy VM.

❓ Configuration

intermediate

Identify the correct health probe configuration for TCP port 80

Which Azure CLI command correctly creates a TCP health probe on port 80 for a load balancer?

A az network lb probe create --resource-group MyRG --lb-name MyLB --name MyProbe --protocol Http --port 80

B az network lb probe create --resource-group MyRG --lb-name MyLB --name MyProbe --protocol Udp --port 80

C az network lb probe create --resource-group MyRG --lb-name MyLB --name MyProbe --protocol Tcp --port 443

D az network lb probe create --resource-group MyRG --lb-name MyLB --name MyProbe --protocol Tcp --port 80

💡 Hint

Check the protocol and port number carefully.

TCP protocol with port 80 is correct for a TCP health probe on port 80. HTTP protocol or other ports do not match the requirement.

❓ Architecture

advanced

Designing backend pools for high availability

You want to design an Azure Load Balancer backend pool to ensure high availability across two regions. Which approach is best?

A Create separate backend pools in each region and use Traffic Manager to route traffic.

B Add all VMs from both regions into a single backend pool on one load balancer.

C Configure backend pools only in the primary region and failover manually.

D Use a single VM in one region as the backend pool to simplify management.

💡 Hint

Consider geographic redundancy and traffic routing.

Using separate backend pools per region with Traffic Manager allows routing users to the closest healthy region, ensuring high availability.

❓ security

advanced

Securing health probes from unauthorized access

How can you secure Azure Load Balancer health probes to prevent unauthorized access to backend VMs?

A Configure Network Security Groups to allow probe IP ranges only on probe ports.

B Disable health probes and rely on manual monitoring.

C Allow all inbound traffic to backend VMs to ensure probes work.

D Use public IP addresses for backend VMs to isolate probes.

💡 Hint

Think about controlling network traffic to only trusted sources.

Network Security Groups can restrict probe traffic to only the load balancer's IP ranges and ports, securing backend VMs from unauthorized access.

✅ Best Practice

expert

Optimizing health probe intervals for backend responsiveness

What is the best practice for setting health probe interval and unhealthy threshold to quickly detect backend failures without causing false positives?

A Set a long interval (60 seconds) and a high unhealthy threshold (10) to reduce load.

B Set a short interval (5 seconds) and a low unhealthy threshold (2) for fast detection.

C Set interval and threshold to 1 to detect failures instantly.

D Disable health probes and monitor backend manually.

💡 Hint

Balance detection speed and avoiding false alarms.

A short interval with a low threshold allows quick detection of failures while avoiding false positives from transient issues.