DNS Resolution Beginner's Guide

　　For beginners to website building or cloud servers, DNS resolution is almost an unavoidable hurdle. Many website owners encounter similar problems: the domain name is purchased, but why is the website still inaccessible? What is the difference between A records and CNAME records? Why does it take so long for DNS changes to take effect? ​​Actually, DNS isn't as complicated as you might think. Once you understand its working principles and combine that with practical experience, you can quickly master it.

　　I. What is DNS? A Simple Explanation

　　DNS stands for Domain Name System. Its core function is singular: to translate human-remembered domain names into computer-readable IP addresses.

　　For example, when you enter www.example.com in your browser, the computer actually accesses 93.xxx.xxx.xxx.

　　DNS is like the internet's "phone book."

　　II. The Complete DNS Resolution Process

　　When a user accesses a website, DNS resolution generally involves the following steps:

　　The browser checks its local cache for domain name records. The operating system queries the local DNS server, which in turn queries the root name servers, and so on, until it reaches the authoritative DNS server, returning the final IP address to the browser.

　　The entire process typically takes milliseconds, but it is a crucial prerequisite for website accessibility.

　　III. DNS Record Types Every Beginner Must Understand

　　In the domain name resolution backend, the various "record types" are the most confusing. Below, we will only discuss the most commonly used and important types for beginners.

　　1. A Record (Most Commonly Used)

　　An A record is used to directly point a domain name to an IPv4 address.

　　Applicable Scenarios: Domain names directly resolved to cloud servers, self-built websites, blogs, backend systems

　　2. CNAME Record (Alias ​​Resolution)

　　A CNAME record is used to point one domain name to another.

　　Common Uses: CDN acceleration, subdomains pointing uniformly to the main domain name

　　Note: A CNAME record cannot exist under the same hostname as an A record.

　　3. MX Record (Essential for Email Services)

　　An MX record is used to specify the address of the mail server. If you use a business email or domain email, you will definitely encounter it.

　　4. TXT Record (Verification Purpose)

　　TXT records are typically used for: domain ownership verification, email anti-spam verification, and third-party service verification.

　　IV. Basic DNS Resolution Configuration Steps

　　The following is a complete beginner's guide using "domain name resolution to a cloud server" as an example.

　　Step 1: Confirm Cloud Server IP

　　In the cloud server console, find your public IPv4 address, for example: 123.45.67.89

　　Step 2: Access the Domain Name Resolution Management Backend

　　Regardless of which platform you purchased your domain name from, there will generally be a "DNS Resolution / Domain Name Resolution" entry.

　　Step 3: Add an A Record

　　Common configurations are as follows:

　　Note: @ represents the main domain, www represents the subdomain.

　　Step 4: Wait for the DNS records to take effect.

　　DNS resolution doesn't take effect immediately; it usually takes several minutes to several hours, with a maximum of 48 hours. This is related to the DNS caching mechanism, and beginners don't need to worry excessively.

　　Ⅴ: What is DNS TTL? Should I change it?

　　TTL represents the time a DNS record is kept in the cache, measured in seconds.

　　Smaller TTL: Faster implementation, but more queries.

　　Larger TTL: Better stability, but slower modification.

　　Beginner's suggestion: Keep the default TTL; frequent adjustments are unnecessary.

　　VI. Common DNS Resolution Errors and Troubleshooting

　　1. Domain name resolution is correct, but the website cannot be accessed.

　　Troubleshooting order: Is port 80/443 open on the cloud server? Is the web service (Nginx/Apache) running? Is the website bound to the corresponding domain name?

　　2. DNS changes have not taken effect.

　　Common causes: Local DNS cache not refreshed, CDN or proxy service being used, TTL setting too high.

　　Test with the following command:

ping example.com
nslookup example.com

　　3. www is accessible, but the main domain is inaccessible.

　　This is usually due to a missing @ record, only a CNAME record, and no A record.

　　VII. DNS Configuration Suggestions for Beginner Website Owners

　　If you are a beginner, remember these principles: prioritize using A records to directly connect to the server, avoid deleting existing records arbitrarily, wait patiently after modifying DNS, and change only one variable at a time for easier troubleshooting.

　　DNS resolution is not an advanced technology, but a fundamental skill for every website owner. Once you truly understand that domain names are for humans, IP addresses are for machines, and DNS connects the two, then DNS will no longer be an obstacle, whether you are building a website, using a CDN, or deploying cloud services.

　　For beginners, understanding DNS is more important than memorizing commands. Once the principles are clear, the operation will always be a matter of details.