Learning IP flow verify diagnostics in Azure Network Watcher

IP Flow Verify is a diagnostic tool in Azure Network Watcher that allows you to verify whether traffic is allowed or denied between two points in your Azure network based on the Network Security Group (NSG) rules.

This tool helps troubleshoot network connectivity issues by checking if the security rules applied to your resources permit or block traffic.

Key Features of IP Flow Verify

1. Traffic Verification

IP Flow Verify helps in confirming whether specific network traffic (such as from a source IP to a destination IP) is allowed or blocked by NSG rules or route tables.

It performs this by simulating the traffic flow and checking how the security rules would apply to that flow.

2. Testing for Specific Traffic

You can specify the direction of traffic (inbound or outbound), the source IP, the destination IP, the protocol (TCP/UDP), and the port number to simulate specific network scenarios.

The tool checks if the traffic would be accepted or denied by the rules defined in NSGs or by other network security configurations.

3. Detailed Diagnostic Results

The diagnostic provides detailed feedback on the result of the test, including:

• Whether the traffic was allowed or denied.

• The specific NSG rule that allowed or denied the traffic.

• Information on the source IP, destination IP, ports, and protocols involved in the flow.

• The network interface(s) involved in the traffic.

4. Simulating Complex Scenarios

IP Flow Verify allows you to test more complex scenarios, such as cross-region traffic, virtual network peering, or traffic from external on-premises systems to Azure.

It takes into account the full network path and any associated security or routing policies.

5. Support for Both IPv4 and IPv6

IP Flow Verify supports both IPv4 and IPv6 traffic, helping you test different versions of IP addressing schemes within your Azure environment.

How It Works

1. When you run IP Flow Verify, it essentially simulates a packet that would flow from the source to the destination.

2. The tool checks the NSG rules applied to the network interfaces involved in the flow.

   • It evaluates whether the specific packet is allowed or denied by looking at the network security policies, route tables, and other related configurations.

3. The diagnostic will then provide you with a pass or fail result and a detailed explanation of the rules applied and any reasons the traffic was blocked.

Example Use Case

Suppose you have a Virtual Machine (VM) in Azure that is unable to communicate with a service on a different VM in the same virtual network.

You could use IP Flow Verify to:

• Specify the source IP (the VM trying to connect) and the destination IP (the VM that the connection is being made to).

• Specify the port (e.g., port 80 for HTTP) and the protocol (TCP).

• Run the test to check if the traffic is being blocked by any NSG rule or if there’s a misconfigured route.

The tool would then tell you whether the traffic is allowed or denied, and if it's denied, it would specify which NSG rule is blocking the traffic.

Benefits of IP Flow Verify

1. Simplifies Troubleshooting

It helps to quickly pinpoint whether traffic is being blocked by NSG rules or other security mechanisms.

2. Reduces Complexity

It saves time by eliminating the need to manually check individual NSG rules and understand their interactions with traffic.

3. Granular Testing

Allows testing specific traffic types (e.g., source, destination, port, protocol) to simulate real-world scenarios and ensure all relevant traffic can flow as intended.

4. Quick Diagnostic Feedback

Provides instant feedback on network security configurations, helping network administrators quickly resolve issues without having to do extensive manual troubleshooting.

Steps to Use IP Flow Verify

1. Navigate to Azure Network Watcher

Go to the Azure portal and select Network Watcher from the "All Services" menu.

2. Select IP Flow Verify

Under the Tools section in Network Watcher, select IP Flow Verify.

3. Input Parameters

• Select the subscription and resource group.

• Choose the network interface or VM from which traffic originates.

• Specify the source IP address and destination IP address.

• Define the protocol (TCP or UDP), the port number, and the direction of the traffic (inbound or outbound).

4. Run the Diagnostic

Click on Check to initiate the diagnostic.

5. Review Results

After the test completes, review the results to see if the traffic is allowed or denied and get details on why the action is being taken.

Use Cases for IP Flow Verify

Troubleshooting Network Connectivity

When you're unsure why traffic is being blocked between Azure resources, IP Flow Verify can confirm whether it's NSG rules or another configuration causing the issue.

Verifying Security Configurations

Ensure that NSGs and other network security policies are configured correctly by testing expected traffic flows.

Validating New Security Policies

Before applying new NSG rules or security settings to your environment, you can use IP Flow Verify to simulate traffic to see how it will be affected.

Cross-Region and Hybrid Connectivity

If you're working with hybrid networks or multi-region architectures, this tool can help validate traffic flows between on-premises and Azure resources or across Azure regions.

Summary

IP Flow Verify is a vital diagnostic tool within Azure Network Watcher that enables network administrators to test and validate network traffic flow through NSGs and other security settings.

By simulating traffic from source to destination and evaluating security policies, it simplifies troubleshooting and helps ensure that network security configurations are properly set up and functioning as intended.