ISIS Accept Policy External

ISISAcceptExt.PNG

  • The ISIS metric type of external can be used instead of internal type
    • Prefix cost (external metric) with lowest cost will be preferred and if prefix cost is the same, the routes are considered ECMP routes
  •  A route-map can be used to specify metric type of none, internal or external; for example, a route-map can be used to selectively set specific routes as external
  • When deciding which routes to add to the route table, a SPB router
    • Internal type routes
      • Always preferred over External type routes
      • Will always prefer the routes with the shortest path internal metric to the BEB node advertising them
      • Will only use the route external cost (prefix-cost) as a tie breaker
      • For route to go into ECMP, both the internal and external metric must be the same
    • External type routes
      • Will only consider the external route metric (prefix-cost)
      • For route to go into ECMP, only the external metric must be the same
  • External metrics is supported as of release 5.0 for the VSP 4000, VSP 8000, and VSP 7200
    • Only IPv4 routes are supported in this release

 

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