A method performed by a control device includes: receiving forwarding information of many network devices in a network, where the many network devices in the network include a first edge device and a second edge device; determining, based on the forwarding information of the second edge device, information about a first network address that is reachable to the second edge device and that is outside the network; and estimating, based on the first network address information and the forwarding information of the plurality of network devices, whether one or more packets whose destination addresses are covered by the first network address information and that enter the network through the first edge device can be forwarded to the second edge device through the network.