Abstract: A communications connection detection method includes sending, by a first network node, a detection request packet to a second network node, where the detection request packet is used to detect whether the first network node and the second network node are in a connected mode, deleting, by the first network node, a next hop resolution protocol (NHRP) table between the first network node and the second network node when the first network node determines that the first network node does not receive a detection response packet sent by the second network node.

Abstract: A method includes obtaining, by a first network device comprising a processor, characteristic information from an encrypted packet received from a second network device based on a determination that the first network device cannot decrypt the encrypted packet. The first network device is free from having an internet protocol security (IPsec) security association (SA), and the second network device has the IPsec SA. The method also includes generating, by the first network device, generating an informational exchange packet when the first network device obtains, based on the characteristic information, an internet key exchange (IKE) SA corresponding to the characteristic information. The informational exchange packet instructs the second network device to delete the IPsec SA on the second network device. The method further includes sending, by the first network device, the informational exchange packet to the second network device.

Abstract: A communications connection detection method includes sending, by a first network node, a detection request packet to a second network node, where the detection request packet is used to detect whether the first network node and the second network node are in a connected mode, deleting, by the first network node, a next hop resolution protocol (NHRP) table between the first network node and the second network node when the first network node determines that the first network node does not receive a detection response packet sent by the second network node.

Abstract: A method includes obtaining, by a first network device comprising a processor, characteristic information from an encrypted packet received from a second network device based on a determination that the first network device cannot decrypt the encrypted packet. The first network device is free from having an internet protocol security (IPsec) security association (SA), and the second network device has the IPsec SA. The method also includes generating, by the first network device, generating an informational exchange packet when the first network device obtains, based on the characteristic information, an internet key exchange (IKE) SA corresponding to the characteristic information. The informational exchange packet instructs the second network device to delete the IPsec SA on the second network device. The method further includes sending, by the first network device, the informational exchange packet to the second network device.