B. It performs tasks that autonegotiation cannot perform.

　　C. It works by exchanging protocol packets between the neighboring devices.

　　D. Both devices on the link must support Unidirectional Link Detection and have it enabled on respective ports.

　　27.What is true concerning Traffic contract, Traffic shaping, and Traffic policing in ATM networks?

　　A. They are parameters of PNNI set during PNNI configuration.

　　B. They are forms of QoS features used in ATM networks.

　　C. They are types of SVCs.

　　D. They are types of PVCs.

　　E. They are only used between ATM switches to control traffic flows.

　　28.Which are the primary reasons to use traffic shaping? (Select two)

　　A. To control the maximum rate of traffic transmitted or received on an interface.

　　B. To control access to available bandwidth.

　　C. To define Layer 3 aggregate or granular incoming or outgoing bandwidth rate limits.

　　D. To control the average queue size by indicating to the end hosts when they should temporarily slow down transmission
of packets.

　　E. To ensure that traffic conforms to the policies established for it.

　　29.In a bridged network running IEEE 802.1d spanning tree, what parameter will a bridge take form the root bridge?

　　A. Maxage

　　B. Forwarding delay

　　C. Hello time

　　D. All of the above

　　30.What statement is FALSE concerning the use of SPAN on the Catalyst 6500?

　　A. It is possible to configure SPAN to have a Gigabit port, such as source port, and a 10/100 port as the destination port.

　　B. If the source port is configured as a trunk port, the traffic on the destination port will be tagged as well, regardless of the configuration on the destination port.

　　C. When a SPAN session is active the destination port does not participate in Spanning Tree.

　　D. With SPAN an entire VLAN can be configured to be the source.

　　E. In one SPAN session it is possible to monitor multiple ports that do not belong to the same VLAN.