Abstract: This application provides a method for updating a route in a network. The first network device sends a first LSA packet to a third network device, so that the third network device generates a first route whose destination address is a second IP address, where a next-hop IP address of the first route is the IP address of the first network device, and the second IP address belongs to the IP network segment corresponding to the first IP address which is an IP address of the first network device. The first network device sends a second LSA packet to the third network device when determining that switching needs to be performed on a next hop of a route in the third network device, whose destination address belongs to the IP network segment, and whose next-hop IP address is the first IP address.

Abstract: This application provides a method for updating a route in a network. The first network device sends a first LSA packet to a third network device, so that the third network device generates a first route whose destination address is a second IP address, where a next-hop IP address of the first route is the IP address of the first network device, and the second IP address belongs to the IP network segment corresponding to the first IP address which is an IP address of the first network device. The first network device sends a second LSA packet to the third network device when determining that switching needs to be performed on a next hop of a route in the third network device, whose destination address belongs to the IP network segment, and whose next-hop IP address is the first IP address.

Abstract: This application provides a method for updating a route in a network. The first network device sends a first LSA packet to a third network device, so that the third network device generates a first route whose destination address is a second IP address, where a next-hop IP address of the first route is the IP address of the first network device, and the second IP address belongs to the IP network segment corresponding to the first IP address which is an IP address of the first network device. The first network device sends a second LSA packet to the third network device when determining that switching needs to be performed on a next hop of a route in the third network device, whose destination address belongs to the IP network segment, and whose next-hop IP address is the first IP address.

Abstract: A bit error information transfer method, a network device, and a communications system are provided, so as to resolve a problem that an existing BFD mechanism cannot be applied to a layer 2 network and cannot be widely applied. In some feasible implementation manners of the application, the method includes: detecting, by a second network device, whether a bit error occurs on a first unidirectional link from a first network device to the second network device; when detecting that a bit error occurs on the first unidirectional link, generating an ISIS packet including bit error information, where the bit error information is used to indicate that the bit error occurs on the first unidirectional link; and sending the ISIS packet to the first network device.

Abstract: This application provides a method for updating a route in a network. The first network device sends a first LSA packet to a third network device, so that the third network device generates a first route whose destination address is a second IP address, where a next-hop IP address of the first route is the IP address of the first network device, and the second IP address belongs to the IP network segment corresponding to the first IP address which is an IP address of the first network device. The first network device sends a second LSA packet to the third network device when determining that switching needs to be performed on a next hop of a route in the third network device, whose destination address belongs to the IP network segment, and whose next-hop IP address is the first IP address.

Abstract: A method for establishing a neighbor relationship, where corresponding authentication information is added to packets that are sent from a first network device and a second network device to each other. The first network device sends a hello packet to the second network device. The second network device receives the hello packet, performs authentication, and responds to the hello packet using an extended unidirectional link (UDL) link state packet (LSP) when the authentication succeeds. The first network device receives the extended UDL LSP, and performs authentication. When an authentication result includes that both the first network device and the second network device enable authentication and the authentication succeeds, a neighbor relationship between the first network device and the second network device may be established.

Abstract: A method for establishing a neighbor relationship, where corresponding authentication information is added to packets that are sent from a first network device and a second network device to each other. The first network device sends a hello packet to the second network device. The second network device receives the hello packet, performs authentication, and responds to the hello packet using an extended unidirectional link (UDL) link state packet (LSP) when the authentication succeeds. The first network device receives the extended UDL LSP, and performs authentication. When an authentication result includes that both the first network device and the second network device enable authentication and the authentication succeeds, a neighbor relationship between the first network device and the second network device may be established.

Abstract: A bit error information transfer method, a network device, and a communications system are provided, so as to resolve a problem that an existing BFD mechanism cannot be applied to a layer 2 network and cannot be widely applied. In some feasible implementation manners of the application, the method includes: detecting, by a second network device, whether a bit error occurs on a first unidirectional link from a first network device to the second network device; when detecting that a bit error occurs on the first unidirectional link, generating an ISIS packet including bit error information, where the bit error information is used to indicate that the bit error occurs on the first unidirectional link; and sending the ISIS packet to the first network device.

Abstract: Embodiments of the present invention provide a method, network device, and system for sending and receiving a packet. The method includes fragmenting, by a first network device, a first Hello packet. Each Hello fragment packet has a fragment ID and a content identifier. The first network device sends fragment brief information of the first Hello packet to a second network device. The fragment brief information of the first Hello packet includes fragment information of each Hello fragment packet. The first network device sends the Hello fragment packet corresponding to the first Hello packet if the first network device receives a request packet sent by the second network device.

Abstract: Embodiments of the present invention provide a method, network device, and system for sending and receiving a packet. The method includes fragmenting, by a first network device, a first Hello packet. Each Hello fragment packet has a fragment ID and a content identifier. The first network device sends fragment brief information of the first Hello packet to a second network device. The fragment brief information of the first Hello packet includes fragment information of each Hello fragment packet. The first network device sends the Hello fragment packet corresponding to the first Hello packet if the first network device receives a request packet sent by the second network device.