Load balancing rules in Azure - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Understanding Azure Load Balancer Rule Behavior

You have an Azure Load Balancer with a rule that forwards TCP traffic from port 80 on the frontend to port 8080 on backend VMs. What happens when a client sends a TCP request to port 80?

A The Load Balancer forwards the request to port 8080 on one of the backend VMs selected by the load balancing algorithm.

B The Load Balancer forwards the request to port 80 on the backend VMs without changing the port.

C The Load Balancer rejects the request because frontend and backend ports must be the same.

D The Load Balancer forwards the request to port 8080 on the client machine.

💡 Hint

Think about how the load balancing rule maps frontend ports to backend ports.

The load balancing rule maps incoming traffic on the frontend port to a specified backend port. Here, port 80 on the frontend is mapped to port 8080 on backend VMs, so traffic is forwarded accordingly.

❓ Configuration

intermediate

Configuring a Load Balancing Rule with Session Persistence

You want to configure an Azure Load Balancer rule to keep client sessions sticky based on the client's IP address. Which setting should you enable in the load balancing rule?

A Set the session persistence to 'Client IP'.

B Set the session persistence to 'Source IP affinity'.

C Set the session persistence to 'Client IP and protocol'.

D Set the session persistence to 'None'.

💡 Hint

Session persistence keeps traffic from the same client going to the same backend VM.

Setting session persistence to 'Client IP' ensures that all requests from the same client IP address are directed to the same backend VM, maintaining session stickiness.

❓ Architecture

advanced

Designing a Load Balancer for High Availability with Multiple Frontend IPs

You need to design an Azure Load Balancer that supports two different public IP addresses for different services but shares the same backend pool. How should you configure the load balancing rules?

A Assign both frontend IPs to a single backend VM without load balancing rules.

B Create one load balancing rule with both frontend IPs assigned to it.

C Create two backend pools, each with its own load balancing rule and frontend IP.

D Create two load balancing rules, each with a different frontend IP configuration but pointing to the same backend pool.

💡 Hint

Each load balancing rule must have one frontend IP configuration.

Each load balancing rule is associated with one frontend IP configuration and one backend pool. To support multiple frontend IPs for different services sharing the same backend pool, create separate rules for each frontend IP.

❓ security

advanced

Securing Load Balancer Rules with Network Security Groups

You have an Azure Load Balancer rule that forwards traffic on port 443 to backend VMs. To ensure only HTTPS traffic is allowed, what must you configure in the Network Security Group (NSG)?

A Allow all inbound traffic to the backend VMs regardless of port.

B Allow inbound traffic on port 443 to the Load Balancer's frontend IP and deny other ports.

C Allow inbound traffic on port 443 directly to backend VMs and deny other ports.

D Deny all inbound traffic to the Load Balancer's frontend IP.

💡 Hint

NSGs control traffic at the network interface or subnet level.

The NSG associated with the backend VMs should allow inbound traffic on port 443 and deny other ports. This ensures only HTTPS traffic reaches the backend VMs, as the Load Balancer forwards traffic to this port.

✅ Best Practice

expert

Optimizing Load Balancer Rules for Backend Health Probes

You want to ensure your Azure Load Balancer only sends traffic to healthy backend VMs. Which configuration is required in the load balancing rule and health probe setup?

A Configure the load balancing rule without a health probe; the Load Balancer automatically detects unhealthy VMs.

B Associate a health probe with the load balancing rule and configure the probe to check the backend VMs' health on a specific port.

C Use a health probe but do not associate it with the load balancing rule; it will still monitor backend health.

D Configure the health probe to check the frontend IP instead of backend VMs.

💡 Hint

Health probes must be linked to load balancing rules to affect traffic distribution.

Health probes monitor backend VM health on a specified port. Associating the probe with the load balancing rule ensures traffic is only sent to healthy VMs.

Practice

1. What is the main purpose of a load balancing rule in Azure Load Balancer?

easy

A. To create virtual machines automatically

B. To store data securely in the cloud

C. To distribute incoming network traffic evenly across backend servers

D. To monitor user activity on a website

Solution

1. Step 1: Understand load balancing rules

   Load balancing rules define how traffic is distributed from the frontend IP to backend servers.

2. Step 2: Identify the main function

   The main function is to spread incoming traffic evenly to avoid overloading one server.

3. Final Answer:

   To distribute incoming network traffic evenly across backend servers -> Option C

4. Quick Check:

   Load balancing rules = distribute traffic evenly [OK]

Hint: Load balancing rules spread traffic evenly to backend servers [OK]

Common Mistakes:

• Confusing load balancing with VM creation
• Thinking it stores data
• Assuming it tracks user activity

2. Which of the following is the correct way to specify a load balancing rule's frontend port in Azure CLI?

easy

A. --frontend-port 80

B. --frontendPort 80

C. --front-port 80

D. --port-frontend 80

Solution

1. Step 1: Review Azure CLI syntax for load balancing rules

   The correct parameter for frontend port is '--frontend-port' with a hyphen.

2. Step 2: Compare options

   Only --frontend-port 80 uses the exact correct syntax '--frontend-port 80'. Others have incorrect parameter names.

3. Final Answer:

   --frontend-port 80 -> Option A

4. Quick Check:

   Azure CLI frontend port = --frontend-port [OK]

Hint: Azure CLI uses hyphenated parameters like --frontend-port [OK]

Common Mistakes:

• Using camelCase instead of hyphens
• Mixing words order in parameter
• Using incorrect parameter names

3. Given this Azure Load Balancer rule configuration snippet:

"frontendPort": 443,
"backendPort": 8443,
"protocol": "Tcp"

What happens when a user sends a TCP request to port 443 on the frontend IP?

medium

A. The request is forwarded to backend servers on port 8443

B. The request is blocked because ports do not match

C. The request is forwarded to backend servers on port 443

D. The request is forwarded using UDP protocol

Solution

1. Step 1: Understand frontend and backend ports in load balancing

   The frontend port is where the client connects; the backend port is where the traffic is sent on backend servers.

2. Step 2: Match the ports and protocol

   Client connects to port 443 (frontend), traffic is forwarded to backend servers on port 8443 using TCP.

3. Final Answer:

   The request is forwarded to backend servers on port 8443 -> Option A

4. Quick Check:

   Frontend port 443 forwards to backend port 8443 [OK]

Hint: Frontend port ≠ backend port; traffic forwards to backend port [OK]

Common Mistakes:

• Assuming frontend and backend ports must be the same
• Confusing TCP with UDP protocol
• Thinking request is blocked due to port difference

4. You created a load balancing rule but traffic is not reaching backend servers. Which of these is a likely misconfiguration?

medium

A. Load balancing rule uses correct protocol and ports

B. Frontend IP address is set correctly

C. Backend pool contains healthy servers

D. Health probe is missing or misconfigured

Solution

1. Step 1: Check role of health probes

   Health probes monitor backend server health; without them, load balancer may not send traffic.

2. Step 2: Identify misconfiguration

   If health probe is missing or wrong, backend servers appear unhealthy, so traffic is blocked.

3. Final Answer:

   Health probe is missing or misconfigured -> Option D

4. Quick Check:

   Missing health probe blocks traffic [OK]

Hint: Always configure health probes to allow traffic flow [OK]

Common Mistakes:

• Ignoring health probe setup
• Assuming backend servers are always healthy
• Overlooking frontend IP correctness

5. You want to create a load balancing rule that forwards HTTPS traffic from port 443 on the frontend IP to port 8443 on backend VMs, but only if the backend VMs pass a TCP health probe on port 8443. Which configuration is correct?

hard

A. Load balancing rule with frontendPort=8443, backendPort=443, protocol=Tcp; health probe on port 443 using Http

B. Load balancing rule with frontendPort=443, backendPort=8443, protocol=Tcp; health probe on port 8443 using Tcp

C. Load balancing rule with frontendPort=443, backendPort=443, protocol=Udp; health probe on port 8443 using Tcp

D. Load balancing rule with frontendPort=443, backendPort=8443, protocol=Tcp; no health probe configured

Solution

1. Step 1: Match frontend and backend ports with protocol

   Frontend port 443 (HTTPS) forwards to backend port 8443 using TCP protocol, matching the requirement.

2. Step 2: Configure health probe correctly

   Health probe must check TCP on port 8443 to verify backend VM health before forwarding traffic.

3. Step 3: Verify other options

   Load balancing rule with frontendPort=8443, backendPort=443, protocol=Tcp; health probe on port 443 using Http swaps ports and uses HTTP probe incorrectly; Load balancing rule with frontendPort=443, backendPort=443, protocol=Udp; health probe on port 8443 using Tcp uses UDP protocol wrongly; Load balancing rule with frontendPort=443, backendPort=8443, protocol=Tcp; no health probe configured lacks health probe, risking traffic to unhealthy VMs.

4. Final Answer:

   Load balancing rule with frontendPort=443, backendPort=8443, protocol=Tcp; health probe on port 8443 using Tcp -> Option B

5. Quick Check:

   Correct ports, protocol, and health probe = Load balancing rule with frontendPort=443, backendPort=8443, protocol=Tcp; health probe on port 8443 using Tcp [OK]

Hint: Match frontend/backend ports and use health probe on backend port [OK]

Common Mistakes:

• Swapping frontend and backend ports
• Using wrong protocol (UDP instead of TCP)
• Skipping health probe configuration