摘要：对于【网络工程师】软考考试而言，试题无疑是最重要的学习资料之一。在软考备考过程中，吃透试题、掌握试题所考知识点、熟悉试题的出题思路，对我们提升分数的效果是最明显的，通过对试题的反复练习，还可以查漏补缺。今天，给大家带来【2018年11月 网络工程师 上午题】部分试题的详解，一起来看看吧~



1、如下图所示，用基本ACL限制FTP访问权限，从给出的Switch的配置文件判断可以实现的策略是( )。①PC1在任何时间都可以访问FTP②PC2在2018年的周一不能访问FTP③PC2在2018年的周六下午3点可以访问FTP④PC3在任何时间不能访问FTP
A、 ①②③④
B、 ①②④
C、 ②③
D、 ①③④

答案:A
答题解析:

华为官方说法：
1）使用在配置ACL生效时间段时，配置的时间段时间不能早于当前时间，否则不会生效。
2）可为多个时间段配置相同的时间段名称，共同来描述某个特殊时间。
3）通过名称来引用一个时间段时，如果该时间段配置了多个生效时间，生效原则为各周期时间段之间以及各绝对时间段之间分别取并集之后，再取二者的交集作为最终生效的时间范围。
本题中只有两个时间范围，一个是周期时间，另一个是绝对时间，因此最终的时间是是这两个范围的交集。时间段ftp-access为2018年每个周末的14:00-18:00。
2和3不冲突，这一点要注意。

2、The TTL field was originally designed to hold a time stamp, which was decremented by each visited router. The datagram was (请作答此空) when the value became zero. However, for this scheme, all the machines must have synchronized clocks and must know how long it takes for a datagram to go from one machine to another. Today, this field is used mostly to control the ( ) number of hops (routers) visited by the datagram. When a source host sends the datagram, it ( ) a number in this field. Each router that processes the datagram decrements this number by 1. If this value, after being decremented, is zero, the router discards the datagram.This field is needed because routing tables in the Internet can become corrupted.A datagram may travel between two or more routers for a long time without ever getting delivered to the ( ).This field limits the ( ) of a datagram.
A、received
B、discarded
C、rejected
D、tansferred

答案:B
答题解析:TTL的基本概念。

3、The TTL field was originally designed to hold a time stamp, which was decremented by each visited router. The datagram was ( ) when the value became zero. However, for this scheme, all the machines must have synchronized clocks and must know how long it takes for a datagram to go from one machine to another. Today, this field is used mostly to control the (请作答此空) number of hops (routers) visited by the datagram. When a source host sends the datagram, it ( ) a number in this field. Each router that processes the datagram decrements this number by 1. If this value, after being decremented, is zero, the router discards the datagram.This field is needed because routing tables in the Internet can become corrupted.A datagram may travel between two or more routers for a long time without ever getting delivered to the ( ).This field limits the ( ) of a datagram.
A、maximum
B、minimum
C、exact
D、certain

答案:A
答题解析:TTL的基本概念。

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