What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags

View all Tags

Is PRTG producing network traffic on UDP port 137?



I did a fresh install of Windows 2003 server and installed PRTG ver. On my firewall, I am seeing lots of UDP port137 traffic from the PRTG server and going to external IPs on the Internet. PRTG is configured to monitor a mirrored port on the switch which is connected to the internal interface of my firewall. It is also configured to monitor certain ports on my switch via SNMP. Why is this?

monitor prtg udp137

Created on Oct 4, 2010 2:04:18 PM

Last change on Oct 15, 2010 2:35:14 PM by  Daniel Zobel [Product Manager]

1 Reply

Accepted Answer




do you use Packet Sniffing and TopLists? If so, the traffic you see on port 137 are DNS requests so that PRTG can translate the IPs in the TopLists to DNS names.



Created on Oct 7, 2010 8:30:18 AM by  Aurelio Lombardi [Paessler Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.