This article applies to PRTG Network Monitor 19.2.50 and later.

The Npcap Loopback Adapter and Additional Services

As of PRTG 19.2.50, Packet Sniffer and Packet Sniffer (Custom) sensors use the Npcap library instead of the deprecated WinPcap library to monitor your traffic. With version 19.2.50, PRTG also installs a loopback adapter as part of this Npcap library. If the system on which your remote probe is installed also runs additional services, for example, a DHCP server, this adapter might result in unexpected behavior.

Possible Errors because of Installed Npcap Loopback Adapter

The following errors might occur because of an installed Npcap loopback adapter:

• EXE sensor timeout errors (for example, VMware sensors, Windows Updates Status (PowerShell) sensors, or HTTP XML/REST Value sensors)
• Error messages:
  • Cannot get hostname (DNS issue)
  • Cannot resolve DNS (DNS issue)
  • Cannot get IP address (DHCP issue)
• Flow issues

Tips for Troubleshooting

To solve these issues, you need to manually uninstall the Npcap loopback adapter:

1. Right-click the Windows start button and select Device Manager.
2. Click the > arrow next to Network adapters to open a list of currently installed network adapters.
3. Right-click Npcap Loopback Adapter and select Uninstall device.
4. Click Uninstall to start the uninstall process.

Note: With PRTG version 19.x.51, the Npcap loopback adapter will not be automatically installed anymore. If you directly upgrade to this version without upgrading to version 19.x.50 first, PRTG will not install the Npcap loopback adapter.