A transmission device is included in a communication network, and the transmission device includes a link trace frame transfer unit that transfers, from a first transferring port corresponding to an operation system route, a first link trace frame that is received and that is destined to a target transmission device, and that transfers, from a second transferring port corresponding to a preliminary system route, a second link trace frame that is distinguishable from the first link trace frame, when transferring ports of the transmission device have a route redundancy configuration; and a link trace response frame transmission unit that transmits, in response to receiving the second link trace frame, a second link trace response frame to an origin transmission device, the second link trace response frame being distinguishable from a first link trace response frame that is transmitted in response to receiving the first link trace frame.