题库第80题求助，谢谢！

CHEN_QingSong

  

QUESTION 80

Which statements describe the routingprotocol OSPF? (Choose three.)

A. It supports VLSM.

B. It is used to route between autonomoussystems.

C. It confines network instability to onearea of the network.

D. It increases routing overhead on the network.

E. It allows extensive control of routingupdates.

F. It is simpler to configure than RIP v2.

  题库答案是 ACE  但是，我看红头发的视频讲解答案是ACD，而且、我也觉得是ACD，求大神帮忙讲解一哈，在此谢过。感谢！！！

CHEN_QingSong

  在线等

zhenqiangbill

OSPF分层结构不会增加上层路由吧，减少还差不多。我觉得D不对。我也是初学者，还是等大神吧。

乱了江湖

个人选E


在ospf中，通过不同区域特性对不同的LSA（链路状态通告）进行限制，极大的减少了其数量。而在ospf中路由更新是通过LSA传递进行共享的。这样就完成了对路由更新的控制。

正如上面说的，既然对路由更新有相应的控制措施，那么D中的增加网络负担就不是很准确了，毕竟增加也是要有个对比的，全是静态路由还没有更新动态呢。

乱了江湖

嗯  区域和LSA 在NP中会有学习。

CHEN_QingSong

zhenqiangbill 发表于 2012-8-30 16:45
OSPF分层结构不会增加上层路由吧，减少还差不多。我觉得D不对。我也是初学者，还是等大神吧。

  ospf 每台路由器构建自己的拓扑数据库 cpu压力会很大  我觉得还是选D

CHEN_QingSong

乱了江湖 发表于 2012-8-31 15:15
嗯  区域和LSA 在NP中会有学习。

  嗯

CHEN_QingSong

乱了江湖 发表于 2012-8-31 15:15
个人选E

  大神言之有理，谢谢！

zhenqiangbill

CHEN_QingSong 发表于 2012-8-31 19:00
ospf 每台路由器构建自己的拓扑数据库 cpu压力会很大  我觉得还是选D

OSPF之所以要分层结构我觉得有一部分是因为为了减少路由,不是增加

baidu1230

ospf 虽然比rip 增加cpu 使用率的overhead 但是这道题说的是增加routing overhead on the network  
所以我觉得是错的

This of course leads to more complexity in the configuration and troubleshooting of OSPF networks. Administrators that are used to the simplicity of RIP are challenged with the amount of new information they have to learn in order to keep up with OSPF networks. Also, this introduces more overhead in memory allocation and CPU utilization. Some of the routers running RIP might have to be upgraded in order to handle the overhead caused by OSPF.

The OSPF protocol is based on link-state technology, which is a departure from the Bellman-Ford vector based algorithms used in traditional Internet routing protocols such as RIP. OSPF has introduced new concepts such as authentication of routing updates, Variable Length Subnet Masks (VLSM), route summarization, and so forth.

如果ospf的overhead会增加的话，那ospf的converges 不会比rip快的。这只是我的个人想法
RIP converges slower than OSPF. In large networks convergence gets to be in the order of minutes. RIP routers go through a period of a hold-down and garbage collection and slowly time-out information that has not been received recently. This is inappropriate in large environments and could cause routing inconsistencies.

一下参考
OSPF Design Guide'
http://www.cisco.com/en/US/tech/ ... 86a0080094e9e.shtml

CHEN_QingSong

baidu1230 发表于 2012-8-31 22:46
ospf 虽然比rip 增加cpu 使用率的overhead 但是这道题说的是增加routing overhead on the network  
所以我 ...

  谢谢您！