642-811 Building Cisco Multilayer Switched Networks (BCMSN) Practice Exam

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642-811 Building Cisco Multilayer Switched Networks (BCMSN)

Note 1: 642-811 Exhibit and all related diagrams are not shown in demo questions.
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Demo Question 1.

Four EliteCertify switches are connected together as shown below: All the ports in the diagram all have the same spanning-tree cost and they're all configured as access ports. If you wanted to use UplinkFast to improve convergence time after link failure; where should you configure UplinkFast?

A. Switch CK1
B. Switch CK2
C. Switch CK3
D. Switch CK4

Display Answer

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Answer: A

Explanation: Note: The UplinkFast feature provides fast convergence in the network access layer after a spanning tree topology change by using uplink groups. UplinkFast accelerates the choice of a new root port when a link or switch fails or when STP reconfigures itself. The UplinkFast feature is designed to run in a switched environment when the switch has at least one alternate/backup root port (port in blocking state), that is why Cisco recommends that UplinkFast be enabled only for switches with blocked ports, typically at the access-layer. Do not use on switches without the implied topology knowledge of an alternative/backup root link typically to distribution and core switches in Cisco multilayer design. In this example, switch CK4 will become the root switch, since it has the lowest bridge priority. Therefore, uplink fast should be configured on switch CK1 . Reference: http://www.cisco.com/en/US/tech/ CK3 89/ CK6 21/technologies_tech_note09186a0080094641.shtml#uplink_fast_fa