The Choices Behind DNS Settings: More Than Just Two Numbers

When you open your network settings and see the blank input boxes for "Preferred DNS" and "Alternate DNS," have you ever hesitated for a moment? Should you enter the string of numbers automatically assigned by your ISP, or the commonly used "8.8.8.8"? This small choice actually determines how and how efficiently you "ask for directions" on the internet, with far more profound implications than you might imagine. This seemingly basic operation relates to your internet speed, security, and privacy.

To understand how to fill in the information, you first need to understand what they do. When you try to access a website, your device doesn't know which specific server on the internet corresponds to the friendly name "www.example.com." It needs to query a dedicated "address lookup service"—the Domain Name System (DNS) server. This server is like a huge, constantly updated phone book, responsible for translating domain names into IP addresses that computers can understand (such as `192.0.2.1`). The "Preferred DNS" is the first "inquiry point" your device consults. When it's working properly and can provide an answer, everything goes smoothly. However, if the primary server fails, responds extremely slowly, or cannot resolve a domain name, your device won't simply give up. This is where the value of a "backup DNS" comes in. It automatically and seamlessly redirects queries to the backup server, ensuring the continuity and reliability of network access. Together, these two form a simple failover mechanism, the first line of defense for network resilience.

So, what should you fill in for these two fields? There are three main categories of options, each representing a different priority and trust choice.

The first category, and the default choice: your Internet Service Provider's (ISP) DNS server. This is usually automatically obtained by the router from the ISP and distributed to your device. Its biggest advantage is its "close physical distance." Because the server is within the ISP's network, resolving frequently accessed websites, especially local ones, is often very fast and has low latency. However, its potential problems include: inconsistent stability; some ISPs may forcibly redirect you to an advertising page when resolution fails; potential congestion during peak hours; and they usually log your queries completely for network analysis or other purposes.

The second category: global public DNS services. This is the choice for most tech enthusiasts and users who prioritize stability. The most well-known is Google Public DNS (`8.8.8.8` and `8.8.4.4`). Leveraging Google's global infrastructure, it offers extremely high resolution speeds and stability, and can redirect your requests to the nearest data center via anycast technology. It supports DNSSEC, helping to prevent DNS spoofing attacks. However, its core controversy lies in privacy, although Google claims to anonymize query data to a limited extent.

Another mainstream option is Cloudflare DNS (`1.1.1.1` and `1.0.0.1`). It touts "faster speeds" and "stronger privacy protection," promising never to use query data for advertising and to purge all logs within 24 hours. This is an attractive option for users who highly value privacy. Other options include OpenDNS (`208.67.222.222` and `208.67.220.220`, now owned by Cisco), which offers robust home protection features, automatically blocking known malware and phishing websites.

The third category focuses on DNS services with specific value propositions. For example, Quad9 (`9.9.9.9`) prioritizes security, directly blocking access to known malicious domains and phishing websites during the resolution phase by linking with multiple threat intelligence sources. This is an excellent choice if you prioritize your family's network security. For users who primarily access domestic websites and services, since the servers are located in China, the resolution path for domestic websites is optimized, potentially resulting in faster access speeds than international services and avoiding possible cross-border latency and blocking issues.

Understanding the options, the configuration itself is quite simple. You can configure it at two levels, with drastically different effects.

Personal Device Configuration: Directly modify the settings on your computer or mobile phone, affecting only that device. In Windows network adapter properties, find "Internet Protocol Version 4 (TCP/IPv4)," select "Use the following DNS server addresses," and then enter the correct information. The process is similar in macOS or Linux network settings.

Router-Level Configuration: This is the more recommended, one-time solution. Log in to your home router's management interface (usually by entering `192.168.1.1` or a similar address in your browser). Locate the DNS server option in the "Network Settings" or "DHCP Server" section. Enter your chosen primary and secondary DNS addresses, save, and restart the router. Afterward, all devices accessing the internet through this router (phones, computers, smart TVs) will automatically use the new DNS, eliminating the need for individual configuration.

How do you verify that the configuration is working correctly? A simple method is to use the command-line tools built into your operating system.

In Windows Command Prompt or PowerShell, you can use the `nslookup` command to query any domain name. It will explicitly tell you which DNS server is being used for resolution.

nslookup www.example.com

The address displayed after "Server:" in the command output is the DNS server you are currently using.

In the terminal of macOS or Linux, the `dig` command provides more detailed information.

dig www.example.com

Check the line after "SERVER:" in the output; you'll see the DNS server address being used.

In short, there's no single right answer to the question, "What should I fill in for the preferred and alternate DNS?" It's not a simple fill-in-the-blank question, but rather a choice based on your different weights of speed, security, privacy, and reliability.