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Collect data using Network Monitor

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In this article, you'll learn how to use Microsoft Network Monitor 3.4, which is a tool for capturing network traffic.

Applies to:   Windows 10

Note

Network Monitor is the archived protocol analyzer and is no longer under development. Also, Microsoft Message Analyzer (MMA) was retired and its download packages were removed from microsoft.com sites on November 25, 2019. There is currently no Microsoft replacement for Microsoft Message Analyzer in development at this time. For similar functionality, consider using another, non-Microsoft network protocol analyzer tool. For more information, see Microsoft Message Analyzer Operating Guide.

To get started, download Network Monitor tool. When you install Network Monitor, it installs its driver and hooks it to all the network adapters installed on the device. You can see the same on the adapter properties, as shown in the following image:

Screenshot of the network adapters properties.

When the driver gets hooked to the network interface card (NIC) during installation, the NIC is reinitialized, which might cause a brief network glitch.

To capture traffic

  1. Run netmon in an elevated status by choosing Run as Administrator.

    Screenshot of Start search results for Netmon.

  2. Network Monitor opens with all network adapters displayed. Select the network adapters where you want to capture traffic, select New Capture, and then select Start.

    Screenshot of the New Capture option on the network monitor menu.

  3. Reproduce the issue, and you'll see that Network Monitor grabs the packets on the wire.

    Screenshot of the Frame summary of network packets.

  4. Select Stop, and go to File > Save as to save the results. By default, the file will be saved as a .cap file.

The saved file has captured all the traffic that is flowing to and from the selected network adapters on the local computer. However, your interest is only to look into the traffic/packets that are related to the specific connectivity problem you're facing. So you'll need to filter the network capture to see only the related traffic.

Commonly used filters

  • Ipv4.address=="client ip" and ipv4.address=="server ip"
  • Tcp.port==
  • Udp.port==
  • Icmp
  • Arp
  • Property.tcpretranmits
  • Property.tcprequestfastretransmits
  • Tcp.flags.syn==1

Tip

If you want to filter the capture for a specific field and do not know the syntax for that filter, just right-click that field and select Add the selected value to Display Filter.

Network traces that are collected using the netsh commands built in to Windows are of the extension "ETL". However, these ETL files can be opened using Network Monitor for further analysis.

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