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Difficulty: EasyApplication Load Balancing and Delivery

You are designing a regional TCP-based application infrastructure. You deploy a Standard Azure Load Balancer to distribute inbound traffic across a backend pool of Azure Virtual Machines in a single virtual network. However, when you attempt to add the virtual machines to the backend pool, the configuration fails validation. Which of the following is the most likely cause of this validation failure?

  1. The virtual machines are associated with Basic SKU public IP addresses.Answer
  2. B
    The virtual machines are configured with User Defined Routes (UDRs) that overlap with the default Azure system routes.
  3. C
    The configuration attempts to route traffic to the backend pool using an Azure Traffic Manager profile.
  4. D
    The Network Security Group (NSG) on the subnet uses individual IP addresses instead of Service Tags for inbound rules.

Answer

The virtual machines are associated with Basic SKU public IP addresses.
The correct option is correct because Azure Standard Load Balancer requires all resources in the backend pool to match its SKU tier. If the virtual machines have Basic SKU public IP addresses attached to their network interfaces, the configuration will fail verification due to SKU mismatch constraints.

Step-by-Step Solution

1
Identify the load balancer SKU being deployed.
The scenario specifies a Standard Azure Load Balancer.
Standard Load Balancers have strict SKU matching requirements for backend resources.
2
Check the SKU requirements for virtual machines in the backend pool.
All virtual machine network interfaces (NICs) and their associated public IP addresses must be Standard SKU.
Standard SKU load balancers do not support mixing Basic SKU public IPs within the same backend pool.
3
Determine the cause of the configuration failure.
The virtual machines are using Basic SKU public IP addresses, preventing successful backend pool association.
Upgrading the public IPs to Standard SKU or removing them is required to resolve the validation failure.

Key Concept

Azure Load Balancer SKU boundary and compatibility constraints
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Topics

Application Load Balancing and Delivery

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