A communication apparatus configured to communicate with a router included in a first network and a multiplexer that multiplexes a plurality of optical signals having different wavelengths transmitted from the communication apparatus, the communication apparatus comprising a memory, and a processor coupled to the memory and configured to transmit and receive a first signal to and from the router, transmit and receive a second signal to and from another communication apparatus in a second network through the multiplexer, the second signal having a transmission scheme different from the first signal, mutually convert the first signal and the second signal with each other, detect a first communication disabled state between the another communication apparatus and the communication apparatus, and transmit, to the router, a first detection signal for detecting adjacency relationship between the communication apparatus and the router when the first communication disabled state is detected.