You can only attach virtual machines that are in the same location and on the same virtual network as the LB.
Virtual machines must have a standard SKU public IP or no public IP.
The LB needs to be a standard SKU to accept individual VMs outside an availability set or vmss. VMs do not need to have public IPs but if they do have them they have to be standard SKU. Vms can only be from a single network. When they don't have a public IP they are assigned an ephemeral IP.
Also, when adding them to a backend pool, it doesn't matter in which status are the VMs.
Note: Load balancer and the public IP address SKU must match when you use them with public IP addresses.

Explanation:

To configure an Azure Standard Load Balancer to distribute HTTPS (TCP port 443) traffic between two virtual machines (vm1 and vm2), several specific configuration steps must be followed according to Microsoft Azure Administrator documentation ("Load Balancer Standard SKU - configuration and differences").
* Remove the public IP addresses from vm1 and vm2:Azure Standard Load Balancer only supports backend resources that use private IP addresses. Virtual machines that are part of a Standard Load Balancer backend pool must not have their own Basic Public IP addresses. Therefore, both vm1 and vm2 must have their public IPs removed before they can be added to the load balancer backend pool.
* Create a health probe and backend pool on lb1:A health probe is required to monitor the availability of backend VMs. The backend pool defines which VMs receive load-balanced traffic. In this case, vm1 and vm2 are added to the backend pool.
* Create a load balancing rule on lb1:The load balancing rule defines how traffic is distributed - specifying frontend IP configuration, protocol (TCP), port (443), backend pool, and health probe.
This configuration allows lb1 to evenly distribute HTTPS traffic across vm1 and vm2, ensuring high availability and secure connectivity using the Standard Load Balancer's internal/private endpoints.

This question focuses on how to monitor network connectivity and latency between Azure virtual machines and on-premises resources using Azure Network Watcher - Connection Monitor (v2).
# Scenario Breakdown
VM1: Azure virtual machine (in your subscription)
DC1: On-premises domain controller (in your datacenter)
Connectivity: Via ExpressRoute
Goal: Use Connection Monitor to track network latency between VM1 (Azure) and DC1 (on-premises) To achieve this, both endpoints (VM1 and DC1) must have agents capable of collecting and sending network telemetry data to Azure Monitor.
# Understanding Azure Connection Monitor (v2)
According to Microsoft Learn ("Monitor network connectivity with Connection Monitor"):
"Connection Monitor (v2) enables you to monitor network connectivity between Azure and on-premises resources. You can monitor connections between Azure VMs, Azure Arc-enabled servers, and any endpoint reachable over TCP or ICMP." To participate in a hybrid connection, the on-premises machine must be onboarded to Azure Arc.
Azure Arc connects your non-Azure servers to Azure Resource Manager and allows management and monitoring using Azure services, including Network Watcher's Connection Monitor.
# Required Agent for On-Premises Monitoring
For on-premises servers (like DC1), Azure Arc uses the Azure Connected Machine agent (formerly known as the Azure Arc agent).
This agent:
Registers the on-premises machine as an Azure Arc-enabled server in Azure.
Enables the use of Azure Monitor, Defender for Cloud, Update Management, and Connection Monitor on that server.
Once the Azure Connected Machine agent is installed and the server is connected through Azure Arc, you can add it as a source or destination endpoint in Connection Monitor to measure latency and packet loss.
# Why Other Options Are Incorrect
Option
Description
Why Incorrect
A). Log Analytics agent
Used for data collection (logs and metrics) for Azure Monitor.
# Does not support Connection Monitor (v2) endpoint monitoring. Deprecated in favor of Azure Monitor Agent.
B). Azure Network Watcher Agent extension
Used only on Azure VMs, not on on-premises servers.
# Cannot be installed on DC1 (non-Azure).
C). Azure Monitor agent extension
Used for telemetry/log ingestion into Azure Monitor.
# Does not support connectivity monitoring for hybrid endpoints.
# D. Azure Connected Machine agent
Connects on-premises servers to Azure Arc, enabling Connection Monitor and other Azure services.
# Correct and required.
# Verification (Microsoft Documentation Extract)
From Microsoft Learn - "Monitor hybrid connectivity using Connection Monitor":
"To monitor on-premises resources, onboard the servers to Azure Arc and install the Azure Connected Machine agent. This agent enables Connection Monitor to collect network connectivity data from on-premises endpoints."
# Final Verified Answer:
D). the Azure Connected Machine agent for Azure Arc-enabled servers
Summary of Key Points
Connection Monitor (v2) can track network latency between Azure and on-premises systems.
On-premises servers must be Azure Arc-enabled using the Azure Connected Machine agent.
Azure VMs use the Network Watcher extension, while non-Azure machines require Azure Arc for integration.
# Correct Answer: D. the Azure Connected Machine agent for Azure Arc-enabled servers

In the provided NSG configuration for VM2, the effective inbound security rules show the following priorities:
Priority
Name
Port
Protocol
Source
Action
100
Allow_131.107.100.50
443
TCP
131.107.100.50
Allow
200
BlockAllOther443
443
TCP
Any
Deny
65000+
Default rules
Various
Any
Allow/Deny
The problem states that connections from 131.107.100.50 to port 443 fail, even though the Load Balancer rules are correct.
The proposed solution is to create a new inbound rule that denies all traffic from 131.107.100.50 with a priority of 64999.
However, this does not solve the problem - it makes it worse, because:
* The rule with priority 64999 has a higher number, meaning it is evaluated later than existing rules.
* Since NSG rules are processed in ascending order of priority, the first matching rule applies.
* The rule at priority 200 (BlockAllOther443) already denies the connection before the new rule is even evaluated.
To fix the issue, the correct solution would be to modify or remove the "BlockAllOther443" rule, or adjust priorities so that the allow rule for 131.107.100.50 is evaluated first.
Simply adding another deny rule with a lower priority number (higher numeric value) will not override existing denies.
# Final Verified Answer: B. No