Introduction about local DNS

[Reginald-Yoeng-Lee]

While setting up v2rayNG, everything is fine but one confusion: what exactly local DNS is?

According to the description of the Enable local DNS option under the VPN Settings section, enabling this option leads to processing DNS by core's DNS module, and it's recommended if we need to route bypass the mainland addresses. Here as far as I'm concerned the core means Xray-core. So here are the questions I couldn't understand.

1. What're the differences exactly between the configurations before and after enabling this option? Why enabling this option may help bypass the addresses?
2. What's the Local DNS port option actually means? What value should I use?
3. Why the VPN server needs to use the DNS server?

If v2rayNG could export or output the final configuration JSON it's applied, most of my questions could be figured out. Sadly it seems it doesn't provide such a feature. So great thanks to anyone who could help.

---

配置v2rayNG时, 有一个问题不太理解, 就是这个 local DNS 到底是什么.

根据 VPN Settings 下面的 Enable local DNS 描述, 开启local DNS可以使用core的DNS模块进行DNS解析, 且如果需要分流国内外流量, 建议开启. 这里core我理解就是Xray-core. 这样就有几个疑问:

1. 开启这个选项会导致v2ray配置文件里哪些选项的变化? 具体配置了什么? 为什么会对流量分流有好处?
2. Local DNS port 这个选项具体是什么意思? 应该填什么值?
3. 为什么VPN server 需要用到DNS解析? 什么场景需要用到?

如果v2rayNG可以预览或导出最终生成的配置JSON, 可以很直观地理解各选项的含义, 可惜貌似没有这种功能, 那除了通读源码外好像就是一个黑盒了. 期盼解惑.