16. What two features in Cisco switches help prevent Layer 2 loops? (Choose two.)
那两个是CISCO交换机的2层防环的功能 A. UniDirectional Link Detection单向链路检测
B. Hot Standby Router Protocol C. Virtual Router Redundancy Protocol D. PortFast E. root guard F. loop guard环路保护
Answer: AF
17. Refer to the exhibit. Which switching feature is being tested?
如图所示，正在测试哪种交换功能?
A. loop guard B. PortFast C. root guard
环路保护
D. BDPU guard
Answer: A
18. In Layer 2 topologies, spanning-tree failures can cause loops in the network. These unblocked loops can cause network failures because of excessive traffic. Which two Catalyst 6500 features can be used to limit excessive traffic during spanning-tree loop conditions? (Choose two.)
在2层的拓扑中，生成树发生故障会导致网络的环路。成环的网络中的流量可以导致网络的 瘫痪。在6500交换机中哪两个功能可以防止生成树的环路过高的流量
A. loop guard
B. storm control
风暴控制 广播抑制
C. storm suppression
D. broadcast suppression
E. BPDU guard
Answer: BD
19. Why does RSTP have a better convergence time than 802.1D?
为什么快速生成树协议收敛时间比802.1d的收敛时间更短
A. it is newer B. it has smaller timers C. it has less overhead D. it is not timer-based
Answer: D
20. Under which two circumstances would an RSTP bridge flush its CAM table? (Choose two.) 在哪两种情况下RSTP桥会刷新MAC地址表 A. upon a port state change
B. upon receiving a topology change notification接到拓扑发生改变的通知
C. when transitioning from discarding to forwarding从丢弃状态过度到转发状态时D. when transitioning from forwarding to discarding E. only when changing from listening to discarding F. when CAM resources have been completely used up
Answer: BC
