如何在Azure中实现On-PREM到Azure IPSEC VPN网关全流量监控？

Got it, let's break down how you can monitor all traffic passing through your Azure VPN gateway between your on-prem network and Azure—including source/destination IPs, ports, and even packet-level details. Here are the key tools and actionable steps to make this happen:

First, turn on diagnostic logs for your VPN gateway—this gives you structured logs that track connection status, tunnel activity, and core traffic details (source/dest IP, port, protocol, and traffic direction).

Steps to enable: #

• Go to your VPN gateway in the Azure Portal
• Under Monitoring, select Diagnostic settings
• Click Add diagnostic setting
• Name the setting, then select all relevant log categories:
  • TunnelDiagnosticLog: Tracks tunnel traffic stats and individual flow details
  • RouteDiagnosticLog: Logs route changes affecting VPN traffic
  • GatewayDiagnosticLog: Captures gateway-level events and errors
• Choose to send logs to a Log Analytics workspace (critical for querying and analyzing data later)
• Save the setting

Querying logs in Log Analytics: #

Use Kusto Query Language (KQL) to filter for the traffic details you need. For example, to get recent tunnel traffic with IP/port info:

AzureDiagnostics
| where ResourceType == "VPNGATEWAYS"
| where Category == "TunnelDiagnosticLog"
| project TimeGenerated, SourceIP, DestinationIP, SourcePort, DestinationPort, Protocol, TrafficDirection, Status
| sort by TimeGenerated desc

If your VPN gateway is connected to a virtual network (VNet) with Network Security Groups (NSGs), enable NSG Flow Logs to get even more detailed traffic records—including allowed/denied flows, and per-flow metadata.

Steps to enable: #

• Go to the NSG associated with your VPN gateway's subnet (or the subnets it connects to)
• Under Monitoring, select Flow logs
• Enable flow logs, set the storage account (or send to Log Analytics), and choose Version 2 (includes more detailed fields)
• Save the setting

Querying NSG flow logs: #

Filter for traffic passing through the VPN gateway by targeting the gateway's public/private IP. Example KQL query:

NSGFlowLogs
| where SubnetName == "GatewaySubnet" // Replace with your gateway subnet name
| project TimeGenerated, SourceIP, DestinationIP, SourcePort, DestinationPort, Protocol, FlowStatus, Direction
| sort by TimeGenerated desc

If you need to inspect actual packet content (not just metadata), use Azure Network Watcher's Packet Capture feature. This lets you capture raw packets going to/from your VPN gateway, which you can analyze with tools like Wireshark.

Steps to set up: #

1. Ensure Network Watcher is enabled in your VPN gateway's region (usually enabled by default, but check in the Azure Portal under Network Watcher)
2. Go to Network Watcher > Packet capture
3. Click Add
4. Name your capture session, select your VPN gateway as the Target resource
5. Set capture filters to narrow down traffic (optional but recommended to avoid large files):
   • Filter by protocol (e.g., UDP port 500 for IKE, IP proto 50 for ESP)
   • Filter by source/destination IP ranges (your on-prem network or Azure VNet ranges)
6. Choose a storage account to save the capture file (.pcap format)
7. Start the capture session, let it run for the duration you need, then stop it

Important note: #

Traffic between your on-prem network and Azure VPN gateway is encrypted via IPsec. So the packets captured on the Azure side will be encrypted ESP packets. To see plaintext data, you'll need to capture packets either:

• On your on-prem network (before encryption or after decryption)
• On an Azure VM within the connected VNet (after the VPN gateway has decrypted the traffic)

To turn all this data into actionable dashboards, use Azure Monitor Workbooks. You can build custom views to track traffic trends, top source/destination IPs, tunnel health, and more.

Quick setup: #

• Go to your VPN gateway > Monitoring > Workbooks
• Select a template (like "VPN Gateway Performance") or create a blank workbook
• Add queries using the KQL examples above, then visualize data with charts, tables, or tiles

Key Considerations #

• Permissions: You'll need roles like Monitoring Contributor or Contributor to enable logs and packet captures
• Cost: Logs and packet capture data consume storage—set retention policies (in diagnostic settings) to control costs
• Encryption: Remember that cross-prem VPN traffic is encrypted, so plaintext data isn't available on the Azure gateway itself

Hope these steps give you full visibility into your VPN gateway traffic. Let me know if you need help with any specific setup step!

内容的提问来源于stack exchange，提问作者Chris