642-801 Building Scalable Cisco Internetworks (BSCI) Testking Exam

Demo Question 6.

Answer: A

Explanation: The original IS-IS specification defines four different types of metrics: cost, delay, expense, and error. The Cisco implementation uses cost only. All links use the metric of 10 by default. The original IS-IS specification defines four different types of metrics. Cost, being the default metric, is supported by all routers. Delay, expense, and error are optional metrics. The delay metric measures transit delay, the expense metric measures the monetary cost of link utilization, and the error metric measures the residual error probability associated with a link. The Cisco implementation uses cost only. If the optional metrics were implemented, there would be a link-state database for each metric and SPF would be run for each link-state database. IS-IS uses a single required default metric with a maximum path value of 1024. The metric is arbitrary and typically is assigned by a network administrator. Any single link can have a maximum value of 64, and path links are calculated by summing link values. Maximum metric values were set at these levels to provide the granularity to support various link types while at the same time ensuring that the shortest-path algorithm used for route computation will be reasonably efficient. IS-IS also defines three optional metrics (costs): delay, expense, and error. Reference: Introduction to Intermediate System-to-Intermediate System Protocol, http://www.cisco.com/warp/public/cc/pd/iosw/prodlit/insys_wp.htm Incorrect