41. Network A has a spanning-tree problem in which the traffic is selecting a longer path. How is the path cost calculated?
网络A 的生成树，其中一条很长的路径，他的成本怎么计算?
A. number of hops B. priority of the bridge C. interface bandwidth D. interface delay E. None of the above
Answer: C
42. You deployed new fibers in your networkto replace copper spans that were too long. While reconnecting the network, you experienced network problems because you reconnected wrong fibers to wrong ports. What could you do to prevent this type of problem in the future, particularly when connecting and reconnecting fiber pairs?
你正在部署你的网络拥光纤来替代过长的铜线路， 在从新联网时你遇到了问题。 因为你错误 的链接了发送接收端口， 你可以做什么来防止以后在发生这样的事情， 特别是在链接一对光 纤的时候
A. Only use fiber in pairs.
B. Configure root guard on your switches.
C. Do not use fiber but use copper.
D. Configure UDLD to prevent one-way link conditions.
配置UDLD来防止单向链路的问题。
Answer: D
43. While deploying a new switch, you accidently connect ports 3/12 and 3/18 together, creating a loop. STP detected it and placed port 3/18 in blocking mode. Why did STP not place port 3/12 in blocking mode instead?
当部署一个新的交换机，你无意的链接了3/12/和3/18，形成了一个环路，STP把3/18端口 设置为阻断端口，为什么没有把3/12设置为阻断端口呢?
A. Port 3/12 was already up and forwarding before the loop was created.
B. Port priority is based on lowest priority and lowest port number. 因为端口ID 3/12比较低
C. You connected the wire on port 3/18 last.
D. None of the above, it is purely random.
Answer: B
44. Two routers configured to run BGP have been connected to a firewall, one on the inside interface and one on the outside interface. BGP has been configured so the two routers should peer, including the correct BGP session endpoint addresses and the correct BGP session hop-count limit (EBGP multihop). What is a good first test to see if BGP will work across the firewall?
有两个运行BGP的路由器连接到防火墙， 一个在inside接口， 一个在outside 接口。 BGP 已经配置并且已经成为了邻居，包含正确的配置了BGP网络地址和正确的BGP跳数的限制 (EBGP的多跳设置)，怎么能够最好的测试BGP工作在防火墙上。
A. Attempt to TELNET from the router connected to the inside of the firewall to the router connected to the outside of the firewall. If telnet works, BGP will work, since telnet and BGP
both use TCP to transport data.
用在inside接口上的路由器telnet 到在outside 接口上的路由器。如果telnet 正常工作侧说明 BGP能正常工作，因为telnet 和BGP 都是使用TCP 来传输数据的
B. Ping from the router connected to the inside interface of the firewall to the router connected to the outside interface of the firewall. If you can ping between them, BGP should work, since BGP uses IP to transport packets.
C. There is no way to make BGP work across a firewall without special configuration, so there is no simple test that will show you if BGP will work or not, other than trying to start the peering session. D. There is no way to make BGP work across a firewall.
Answer: A
45. Refer to the exhibit. In this network, R1 has been configured to advertise a summary route, 192.168.0.0/22, to R2. R2 has been configured to advertise a summary route, 192.168.0.0/21, to R1. Both routers have been configured to remove the discard route (the route to null created when a summary route is configured) by setting the administrative distance of the discard route to 255.
如图所示，在这个网络中，R1通告了192.168.0.0/22的汇总路由给R2， R2通告了192.168.0.0/21的汇总路由给R1。两台路由器都配置了汇总路 由的null0 接口来防止路由的环路。发生什么情况，R1能收到一个去192.16 8.3.1的数据包?
What will happen if R1 receives a packet destined to 192.168.3.1?
A. The packet will loop between R1 and R2. 这个包在R1和R2之间形成了环路
B. It is not possible to set the administrative distance on a summary to 255.
C. The packet will be forwarded to R2, where it will be routed to null0.
D. The packet will be dropped by R1, since there is no route to 192.168.3.1.
Answer: A
