A packet processing method and a gateway device are provided. The method includes: A first gateway device receives, by using a first link, a first one-arm BFD echo packet returned by a network device, where the first one-arm BFD echo packet includes identification information, and the identification information is used to uniquely identify a second gateway device. The first gateway device determines, based on the identification information, to forward the first one-arm BFD echo packet to the second gateway device. The first gateway device sends the first one-arm BFD echo packet to the second gateway device. The network device is multi-homed connected to the first gateway device and the second gateway device. The first gateway device and the second gateway device form a multi-active gateway. According to the method, efficiency of detecting, by using a one-arm BFD echo session in a VXLAN multi-active gateway scenario is improved.