CompTIA Network+

Network+ 的基于表现题目：是什么，如何练习

Network+ 的 PBQ 通常涉及配置与诊断：在拓扑图中放置设备、匹配端口与协议，或者给排查故障的步骤排序。这类题目更青睐真正动手看过网络的人，而不是只读过理论的人。

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考试在考察什么

为什么会有这些题目

反复出现的考点是：你能否对一个从未见过的拓扑进行推理。知道“默认网关的存在”只是记忆，而推断出“流量失败是因为网关处于不同的子网”才是 PBQ 真正要考的能力。

在真实考试中，它们表现为performance-based questions (PBQs)。Multiple-choice (single and multiple response) plus performance-based questions (PBQs)

  • 在动手操作界面之前，先在题目提供的画板上把拓扑画出来。Network+ PBQ 出错，多半是方向搞错了，而不是知识点不会。
  • 逐个协议分析，而不是逐台设备分析。题目通常只卡在某一层，找准是哪一层，问题就会迎刃而解。
  • 留意端口与协议的配对。这是最常见的匹配题类型，也是最容易因为粗心丢分的地方。

Try three questions. Understand every answer.

Original English practice examples, with answers and explanations available here. No account required. These are independent teaching examples, not official exam questions or exam dumps.

Question 1 of 3 · Network architecture and protocols

Small packets cross a VPN, but larger packets fail. A capture shows that fragmentation is blocked, while the physical links remain healthy. Which investigation best targets the size-dependent failure?

Answer and explanation

Best answer: Path MTU and tunnel overhead

Tunnel overhead reduces available packet size. Examine the path MTU and the handling of packets that exceed it before changing unrelated services.

Why the other choices fit less well

DNS caching, application timeout, and DHCP lease duration do not explain a verified packet-size boundary across the tunnel.

IETF: path MTU discovery

Question 2 of 3 · Networking concepts

Which address belongs to an RFC 1918 private IPv4 range and requires an appropriate gateway or translation arrangement to communicate with the public internet?

Answer and explanation

Best answer: 172.20.14.8

172.20.14.8 lies within 172.16.0.0/12, one of the RFC 1918 private ranges. Private addresses are not globally unique public internet addresses.

Why the other choices fit less well

172.32.14.8 is outside 172.16.0.0–172.31.255.255. 192.169.1.8 is outside 192.168.0.0/16, and 11.0.0.8 is outside 10.0.0.0/8.

IETF: private IPv4 address allocation

Question 3 of 3 · Network troubleshooting

One client cannot resolve an internal hostname. It reaches the service by IP, while another client resolves the same name. Which comparison is most useful first?

Answer and explanation

Best answer: The clients’ configured DNS resolvers and their answers

Compare the resolver configuration and query results on the working and failing clients. This tests the observed name-resolution difference without disrupting a reachable service.

Why the other choices fit less well

Display resolution, window size and keyboard layout do not explain the different DNS responses. Broader infrastructure changes would need additional evidence.

Microsoft: test DNS queries with nslookup

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你在这里能得到什么

我们如何练习它们

我们的 Network+ 题库包含 31 道 PBQ 风格练习题，分为两种形式：匹配任务（将每项需求与满足它的能力配对）和排序任务（将某个流程的步骤排序）。每道题都附有和选择题相同的完整解析，说明为什么正确的安排是对的，以及为什么看似合理的选项是错的。

这些练习训练的是考试所考察的推理能力——顺序、定位和匹配——而不是复刻厂商的模拟界面。这里的任何内容都不会重现真实的考试环境，任何练习产品也都不应该合法地这样做。

看看你在 Network+ 上处于什么水平

20 道免费题目，无需信用卡。你的领域得分会显示在预约考试前哪些方面还需要加强。

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有依据地练习

理解答案背后的判断。

先分析情境，找出关键证据，再对照解析检查自己的推理。根据各领域的得分决定下一次复习重点。练习正确率只能提示学习进度，不能预测正式考试成绩，也不等同于官方分数。

最新练习集提供八种语言版本。较早的练习可能以英语显示。这些是独立编写的原创练习情境，并非官方考试题目。