Microsoft AZ-104 Exam - Topic 5 Question 134 Discussion

This question tests understanding of Azure Load Balancer SKU compatibility and backend pool configuration requirements.

Scenario Summary

You have:

VM1 and VM2 in the same VNet (VNET1)

A Load Balancer (LB1) configured as:

Type: Internal

SKU: Standard

You need to ensure that VM1 and VM2 can be added to LB1's backend pool.

The proposed solution:

'You create two Standard public IP addresses and associate a Standard SKU public IP address to the network interface of each virtual machine.'

Understanding Azure Load Balancer Requirements

1. Backend pool requirements for a Standard Load Balancer:

All VMs must be in the same virtual network as the load balancer.

Each VM's NIC must be configured with a Standard SKU IP configuration (private or public).

The Load Balancer SKU must match the SKU of the IP addresses associated with the VM network interfaces.

2. Internal Load Balancer behavior:

An Internal Load Balancer (ILB) distributes traffic within a virtual network using private IP addresses, not public IPs.

Therefore, the backend VMs do not need public IPs --- and adding them does not affect backend pool membership.

3. SKU alignment rule (Microsoft Docs):

''You can only attach virtual machines or instances that use Standard IP configurations to a Standard Load Balancer. Basic and Standard SKUs are not interchangeable.''

However:

A public IP is only required for inbound Internet access or outbound NAT, not for internal load balancing.

For an Internal Standard Load Balancer, backend pool members require Standard SKU NIC configurations, not public IPs.

Why the Proposed Solution Fails

The solution suggests creating two Standard public IPs and assigning them to the VMs' NICs.

This does not enable VM1 and VM2 to join the backend pool of an internal load balancer, because:

The load balancer type is internal, meaning it routes private traffic within the virtual network, not via public IPs.

Backend pool membership depends on the NIC's private IP configuration, not its public IP.

Adding public IPs only exposes VMs to the Internet and does not influence load balancer backend eligibility.

Thus, this action is unnecessary and does not meet the goal.

Correct Solution (for reference)

To meet the goal:

Ensure VM1 and VM2 have NICs configured with Standard SKU private IPs.

Ensure both VMs are in VNet1, the same virtual network as LB1.

No need to assign public IPs to internal backend VMs.

You could also ensure:

az network nic ip-config update

--name ipconfig1

--nic-name VM1-nic

--resource-group RG1

--private-ip-address-version IPv4

--sku Standard

Final Verified Answe r: