---
title: "Flow/Firewall Log Collection"
slug: "flow-firewall-log-collection"
description: "Learn to set up Azure flow and firewall logs for effective network monitoring and analytics with Kentik, enhancing your Azure VNet security and visibility."
updated: 2026-04-29T14:07:52Z
published: 2026-04-29T14:07:52Z
canonical: "kb.kentik.com/flow-firewall-log-collection"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.kentik.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Flow/Firewall Log Collection

This article covers how to set up Azure flow and firewall logs in [**Kentik**](/v1/docs/kentik-for-azure).

## Azure Flow Log Collection

Kentik supports [**Azure flow logs**](https://learn.microsoft.com/en-us/azure/network-watcher/vnet-flow-logs-overview), allowing network traffic data from Azure to be integrated with other sources for visualization, monitoring, alerting, and analytics in the Kentik portal.

![Diagram illustrating a hybrid network architecture with various subnets and gateways.](https://cdn.us.document360.io/082e25b5-afce-42d4-8f47-70bd3f1d02b7/Images/Documentation/Azure-Hybrid_Cloud-299h674w.png)

*An example hybrid network architecture with on-prem and an Azure VNet.*

**Key Points**:

- **Flow Logging Service**:
  - Provided by Azure Monitor under the namespace `Microsoft.Insights`.
  - Flow logs are generated by VNets or NSGs in your Azure subscription.
  - Logs capture ingress and egress traffic and are structured in JSON format (see Azure docs on [**Log format**](https://learn.microsoft.com/en-us/azure/network-watcher/vnet-flow-logs-overview#log-format)).
- **Log Export Process**:
  - Logs are not consumed directly from resources. Instead, they are exported to a storage account that aggregates logs from NSGs/VNets in the same location and resource group.

### NSG Flow Logs vs. VNet Flow Logs

Azure supports the collection of both VNet flow logs and NSG flow logs, as compared here:

- **NSG Flow Logs**: Capture IP traffic flowing through an NSG.
  - NSGs are used to filter network traffic to and from Azure resources in a virtual network.
  - NSG flow logs provide detailed information about each flow, including source and destination IP addresses, ports, protocol, and whether the traffic was allowed or denied by the NSG rule.
  - Offer granular visibility at the NSG level, useful for understanding security group efficacy and troubleshooting access issues for specific subnets or VMs.
- **VNet Flow Logs**: Capture traffic entering and leaving the VNet.
  - Ideal when managing complex network topologies with many NSGs.
  - Simplify troubleshooting and security monitoring for the entire virtual network.

> [!TIP]
> **TIP**: Kentik recommends following Microsoft’s guidance to use VNet flow logs instead of NSG flow logs going forward (see [**Microsoft's flow logging recommendation**](https://learn.microsoft.com/en-us/azure/network-watcher/nsg-flow-logs-overview?tabs=Americas)).

### Azure Flow Log Retention

Managing the retention of Azure flow logs is crucial for minimizing cloud storage costs. Here’s how retention is handled:

- **Retention Setting**: Determines how long each log is kept after creation. It can be configured in two ways:
  - **Via Script (Recommended)**:
    - Default retention is set to two days.
    - Modify the retention duration in the script as described in step #4 of [**Generate PowerShell Script**](/v1/docs/automated-configuration-powershell#generate-powershell-script).
  - **Manual Configuration**: Adjust the **Retention** setting in Azure’s **Flow logs settings** dialog.
- **Retention Range**:
  - Specified as an integer in whole days.
  - Valid range is from 1 to 365 days.

### Enable VNet/NSG Flow Log Export

To enable VNet or NSG flow log export to a storage account, follow these steps:

1. Enable the [**Network Watcher**](/v1/docs/automated-configuration-powershell#azure-script-operations) service in the region where your resources reside:
  1. In the [**Azure Portal**](https://portal.azure.com/), search for and select **Network Watcher**.
  2. Ensure the status for your target region is **Enabled**.
2. Configure the flow logs:
  1. In the Network Watcher menu, select **Flow logs**.
  2. Click **+ Create** to set up a new flow log.
  3. For **Target Resource**, select the VNet or NSG you wish to monitor.
  4. Select the **Storage account** you will use for Kentik.
  5. Finalize the setting to begin the export.

## Azure Firewall Log Collection

In addition to VNet and NSG flow logs, Kentik supports the ingestion of Azure Firewall logs to provide deeper visibility into application and network-level security events.

> [!NOTE]
> **Notes**:
> 
> - Firewall logs must be sent to the **same** **storage account** used for your VNet flow logs.
> - In addition to the Azure docs linked below, see the process steps in [**Enable Firewall Log Export**](/v1/docs/flow-firewall-log-collection#enable-firewall-log-export).

### Supported Firewall Log Types

Kentik can process the following Azure Firewall log types (click a type to view the related Azure doc):

- [**azfwapplicationrule**](https://learn.microsoft.com/en-us/azure/azure-monitor/reference/tables/azfwapplicationrule): Logs for application rules associated with a firewall.
- [**azfwnetworkrule**](https://learn.microsoft.com/en-us/azure/azure-monitor/reference/tables/azfwnetworkrule): Logs for network rules associated with a firewall.
- [**Legacy Azure diagnostics logs**](https://learn.microsoft.com/en-us/azure/azure-monitor/reference/supported-logs/microsoft-network-azurefirewalls-logs): Includes support for `AzureFirewallNetworkRule` and `AzureFirewallApplicationRule`.

### Enable Firewall Log Export

To enable Azure Firewall log export to the **same storage account** used for your VNet/NSG flow logs, follow these steps:

1. Create a diagnostic setting for one or more log categories:
  1. In the [**Azure Portal**](https://portal.azure.com/), navigate to your Azure Firewall resource.
  2. In the left-hand menu under Monitoring, select **Diagnostic settings**.
  3. Click **+ Add diagnostic setting**.
  4. In the Log categories section, select one or more of the following:
    - **azfwapplicationrule**: For application-level filtering logs.
    - **azfwnetworkrule**: For network-level filtering logs.
    - **AzureFirewallNetworkRule** / **AzureFirewallApplicationRule**: If using legacy log formats.
  5. Under Destination details, check the box for **Archive to a storage account**.
  6. Select the **Subscription** and the specific **Storage account** that Kentik is configured to monitor.