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What configuration change can you make to cause IS-IS to select the optimal path based on the interface bandwi

You have just enabled IS-IS on the lab testing network. You notice that IS-IS is not using the
optimal path selection based on the interface bandwidth. Currently, the IS-IS routing process
seems to be selecting the best path based on the hop count.
What configuration change can you make to cause IS-IS to select the optimal path based on the
interface bandwidth?

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A.
Enable a wide-style IS-IS metric.

B.
Enable a narrow-style IS-IS metric.

C.
Change the default auto-cost reference bandwidth to a higher value.

D.
Change the default IS-IS metric on each of the router interfaces to better correspond to the
interface bandwidth.

E.
Change the interface bandwidth by using the bandwidth interface configuration mode
command.

Explanation:
http://bradhedlund.com/notes/is-is/

2 Comments on “What configuration change can you make to cause IS-IS to select the optimal path based on the interface bandwi”

  1. jslaven says:

    http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.shtml#wp39006

    Default Metric

    The Cisco implementation uses cost only.

    While some routing protocols calculate the link metric automatically based on bandwidth (OSPF) or bandwidth/delay (Enhanced Interior Gateway Routing Protocol [EIGRP]),

    ***there is no automatic calculation for IS-IS.***

    Using old-style metrics, an interface cost is between 1 and 63 (6 bit metric value). All links use the metric of 10 by default. The total cost to a destination is the sum of the costs on all outgoing interfaces along a particular path from the source to the destination, and the least-cost paths are preferred.

    The total path metric was limited to 1023 (the sum of all link metrics along a path between the calculating router and any other node or prefix). This small metric value proved insufficient for large networks and provided too little granularity for new features such as Traffic Engineering and other applications, especially with high bandwidth links. Wide metrics are also required if route-leaking is used.

    Extended Metric

    Cisco IOS Software addresses this issue with the support of a 24-bit metric field, the so-called “wide metric”. Using the new metric style, link metrics now have a maximum value of 16777215 (224-1) with a total path metric of 4261412864 (254 x 224).




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