One embodiment of the present invention provides a system for detecting a path between two nodes. During operation, the system transmits a network-testing request frame, which includes a time-to-live (TTL) field within a Transparent Interconnection of Lots of Links (TRILL) header, from a source node to a destination node. In response to receiving a network-testing response frame sent from an intermediate node, the system increments the TTL value by 1 and re-transmits the network-testing frame to the destination node. In response to receiving a network-testing response frame sent from the destination node, the system determines a path between the source node and the destination node. The network-testing request or response frames is not processed on an Internet Protocol (IP) layer.