Methods and apparatus for performing non-intrusive network layer performance measurement in communication networks are disclosed. An example method to measure network layer performance between existing network nodes disclosed herein comprises coupling a first intelligent network interface (INI) to an available access port of a first existing network node providing access to a network, wherein the first INI obtains power and input information only from the access port after being coupled thereto, and exchanging test messages between the first INI and a second INI coupled to a second existing network node during normal operation of the first and second existing network nodes to measure network layer performance, wherein the test messages originate in the first INI and are routed through the first and second existing network nodes using a first network layer address associated with the first INI and a second network layer address associated with the second INI.