Exam 350-501 topic 1 question 427 discussion

The correct answer is B. The headend router starts the invalidation timer to bring the tunnel down. In a segment-routing TE (Traffic Engineering) tunnel environment, when a link is lost and there is no secondary backup path in place, the following happens: The headend router detects the loss of the primary path. Since there is no secondary path configured, the headend router starts an invalidation timer. During the invalidation timer period, the headend router continues to forward traffic using the stale label stack. Once the invalidation timer expires, the headend router declares the tunnel as down and stops forwarding traffic on the tunnel. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/seg_routing/configuration/xe-17/segrt-xe-17-book/m_seg-routing-te-isis.html

should be B When an SR-TE LSP path becomes invalid (e.g., due to a link or node failure), the head-end router invalidates the current path and removes the tunnel forwarding entry if there are no other available and valid path options. This process ensures that traffic is not forwarded over a faulty path and that the tunnel is effectively shut down if no alternative routes exist.