I am really desperate to get an answer on this, as I am wasting a lot of time trying to figure out what the problem is.

Can Cisco switches be configured to block network testers? My network tester behaves extremely erratic when I connect it to a new network switch we installed at work. If you search for NetTool Series II pdf in google you'll get info on what it does, and how it works.

  • Have you checked/swapped cables? Erratic behaviour is commonly due to cables and connectors. Dec 8, 2016 at 10:19
  • Brand new patch cables, and all other devices work OK on the network. The Fluke Network Tester is the only one affected, and only while connected to this switch. Dec 9, 2016 at 20:50

1 Answer 1


Q. Can Cisco switches be configured to block network testers?

A. Yes the switch could be blocking your testing device if the port is configured to only allow specific MAC addresses. See this link ands the following excerpt:

"If a port is configured as a secure port and the maximum number of secure MAC addresses is reached, when the MAC address of a workstation attempting to access the port is different from any of the identified secure MAC addresses, a security violation occurs".

Alternatively, this could be due to the link negotiation (auto negotiation or hard coded) config if the devices are not set to negotiate correctly. Check your docs and have the Network team confirm the current settings for the ports you are using.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .