This application discloses a method and an apparatus for processing a transmission path fault, and a system, to resolve a prior-art problem that a data packet fails to be forwarded because a capacity of a context table supported by a node is insufficient. In this application, after a first network device receives a packet, and when the first network device determines that a third network device is faulty, a difference between an initial value of a segment routing global block SRGB of the first network device and an initial value of an SRGB of the third network device is determined, and a backup path is determined based on the difference and a backup forwarding table. The first network device sends a first packet based on a backup.
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