You are a network administrator at Pcjob. You are troubleshooting a router problem. You issue the show ip route command on one of the routers. The output from the command is shown in the following exhibit:

What does [120/3] represent?

A. 120 is the bandwidth allocation and 3 is the routing process number.
B. 120 is the administrative distance and 3 is the metric for that route.
C. 120 is the value of the update timer and 3 is the number of updates received.
D. 120 is the UDP port for forwarding traffic and 3 is the number of bridges.

　　作為Pcjob的網(wǎng)絡(luò)管理員，你正在為路由器排錯(cuò)，你在其中的一臺(tái)路由器使用show ip route命令，輸出的結(jié)果如上圖，[120/3]描述的是什么意思？

正確答案：B

解釋?zhuān)?/p>

　　路由器的IOS使用一個(gè)名為Administrative Distance(管理距離)的概念來(lái)決定使用哪一個(gè)路由。Admininstrative distance表示的是一個(gè)單獨(dú)路由器中所有路由協(xié)議的可信度的這樣一個(gè)數(shù)值，數(shù)值越低越好，也就是說(shuō)，數(shù)值越低，路由協(xié)議可信度越高。

Route Type Administrative Distance

• Connected 0
• IGRP 100
• RIP 120

參考資料：

CCNA Self-Study CCNA ICND exam certification Guide (Cisco press, ISBN 1-58720-083-X) Page 177