300-510 SPRI: Implementing Cisco Service Provider Advanced Routing SolutionsDemo

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QuestionQ223

Unicast Routing

Refer to the exhibit.

Question Image

A network engineer has configured routers R1 and R5 for IS-IS Level 1 operation and router R6 for IS-IS Level 2 operation. Every other router operates as a Level 1 / Level 2 router. Traffic from R1 to R6 is expected to traverse R2, but IS-IS has calculated the best path through R4. Which action resolves the issue?

  • A Configure all routers as Level 1 routers.
  • B Remove the link metric for the link from router R1 to router R2.
  • C Change the link metric for the link from router R1 to router R2 to 1.
  • D Configure all routers as Level 1 / Level 2 routers.
Explanation

IS-IS prefers the path with the lowest total outgoing-link metric. The route through R4 has a cost of 20 from the two unconfigured links at the default metric of 10, while the route through R2 has a cost of 26 (8 + 8 + 10). Changing the R1–R2 metric to 1 reduces the intended path cost to 19, so it becomes the preferred route. Removing the metric would restore its default value of 10 instead.

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