A method for a network device to access a packet switched network is applied to a system in which the network device accesses the packet switched network by connecting to PEs in an active-standby mode. The method includes: an active PE and a standby PE each sends a fault detection message to the network device through an interface connected to the network device; the active PE sets the state of the interface to “up” and advertises a route to a remote PE if a fault detection response returned by the network device is received through the interface within a preset period; otherwise, the active PE sets the state of the interface to “down” , and withdraws the advertised route; and the standby PE sets the state of the interface to “up” and advertises another route to the remote PE after receiving a fault detection response through the interface connected to the network device.