ccnp求解释

dwzok305

Your network has a mixture of Fast Ethernet and Gigabit Ethernet links. What needs to be done to ensure optimal data routing when using OSPF?
Select the best response.
A. Nothing. OSPF will determine the most optimal path for routing data by default.
B. Adjust the hello and dead timers for more rapid detection of link failures.
C. Increase the reference-bandwidth used to calculate the interface default metrics, on all routers in yournetwork.
D. Set the priority values on every broadcast interface to ensure that the designated and backup
designated routers are the routers with the most processor and memory resources.
Answer: C
Section: OSPF
Explanation/Reference:
考点分析：OSPF
OSPF有个metric值的默认问题，如果是Gbit网就需要更改默认值。
这里讲增大参考带宽值 ，但是 1G增大到40G的话，cost值就是100M/40000M 是不是取整为1.这与100Mfast ethernet的
cost值100M/100M是一样的1？

francisdon

我是这样理解的spf的metric值用10的8次方除以接口带宽，它说修改才考带宽是修改10的八次方的值，不是修改接口带宽。

francisdon

郁闷写ospf竟然多o变成了一个表情！
cost=10^8/bandwidth  
使用路由配置下命令auto-cost reference-bandwidth ，要在所有的路由器下都改，在百兆以上的 网络中推荐使用

箭落星辰

我认为metric的1是一样的，参考带宽的设置应该考虑实际链路情况