What to do if DNS resolution for a domain fails? Common causes and solutions.

　　You can send messages and watch videos on WeChat, but when you open a browser and enter a website address, you just can't access it, getting errors like "Server IP address not found" or "DNS_PROBE_FINISHED_NXDOMAIN". Many people's first reaction is "My internet is down," but upon closer inspection, that doesn't seem right, because all the other apps are working fine. Today, I'll talk about what exactly causes this DNS resolution failure and how to fix it step by step.

　　I. First, figure out: Where exactly is the problem?

　　Before we start, let's take 30 seconds to do a quick assessment. This will save you a lot of time wasting time troubleshooting.

　　Step 1: Check if only specific websites are inaccessible.

　　Try accessing several different websites, such as Baidu, Google (if you can access them), and Taobao. If only one or two websites fail, the problem is most likely with the domain name itself or your hosts file. If all websites fail, then it's a problem with your local network or DNS configuration.

　　Step 2: Test Basic Network Connectivity

　　Open the command prompt (Windows: Win+R, type cmd, press Enter), and type: ping 8.8.8.8

　　If this command succeeds (i.e., you get a response), your physical network connection is good, and the problem is indeed stuck in the DNS resolution stage. If even this fails, you need to check the network cable, Wi-Fi, or router.

　　Step 3: Check if it's a Browser Issue

　　Try a different browser, or try connecting to the same Wi-Fi network with your phone. If your phone can access the network but your computer can't, the problem lies on your computer, not the router or your ISP.

　　After completing these three steps, you should have a general idea of ​​the problem's direction. Below, we'll go through the possible causes and solutions one by one, from simplest to most complex.

　　II. Five Most Common Causes and Solutions

　　Based on my experience, 80% of DNS resolution problems fall into one of the following categories. Let's list them in descending order of frequency.

　　1. Local DNS Cache "Remembers Incorrectly"

　　This is the most common cause and also the easiest to solve. To speed up internet access, your computer caches resolved domain names and IP addresses. However, sometimes this cache is "incorrect" or "expired," and the computer foolishly tries to access the internet using the old information, resulting in failure.

　　Solution (Finishes in 10 seconds):

　　Windows users: Open Command Prompt as administrator, type `ipconfig /flushdns` and press Enter.

　　Mac users: Open Terminal, type `sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder`

　　Linux users: Type `sudo systemd-resolve --flush-caches`

　　After executing these commands, refresh the webpage. In many cases, this one step solves the problem.

　　2. Incorrect DNS Server Address Configuration

　　If refreshing the cache doesn't work, check if your computer is pointing to a non-existent or malfunctioning DNS server.

　　This usually happens when: you manually changed your DNS settings (e.g., to bypass internet restrictions or speed up your connection), but that DNS provider later has problems; or you used proxy software, which changed your DNS settings but didn't revert them.

　　Solution: Change your DNS to automatic acquisition, or switch to a stable and reliable public DNS.

　　Windows steps: Control Panel → Network and Sharing Center → Change adapter settings → Right-click your network connection → Properties → Double-click "Internet Protocol Version 4 (TCP/IPv4)" → Select "Obtain DNS server address automatically"

　　3. Hosts File Hijacked

　　This is a slightly more subtle problem. The Hosts file is like a local phone book on your computer, with higher priority than the DNS server. Some software (or viruses) write random things into the hosts file, pointing domains like Taobao and Baidu to incorrect IP addresses, or even to 127.0.0.1 (which is yourself), making them inaccessible.

　　Solution: Open the hosts file with Notepad:

　　Windows path: C:\Windows\System32\drivers\etc\hosts

　　Mac/Linux path: /etc/hosts

　　Note: Windows users need to open Notepad "as administrator" before opening this file; otherwise, it won't save.

　　After opening, you'll see a bunch of text. Look for the domain you can't access, or any entries that seem suspicious (like "127.0.0.1 www.baidu.com"). Delete the suspicious lines, save the file, refresh the page, and try again.

　　4. Router malfunction or ISP DNS failure

　　If the above three steps don't work, the problem might be with your router or your broadband provider. If a router isn't restarted for a long time, its cache and state may become corrupted. More commonly, many routers default to using the DNS server provided by their broadband provider, which sometimes experiences regional failures or very slow response times.

　　Solution: First, restart the router—unplug it, wait 30 seconds, and then plug it back in. This seemingly simple step can sometimes solve most problems. If restarting doesn't work, log in to the router's management interface (usually by entering 192.168.1.1 or 192.168.0.1 in your browser), find the DHCP settings or DNS settings, and change the DNS server to one of the previously recommended public DNS servers (e.g., 114.114.114.114). Then save and restart the router. This will benefit all your devices in the house.

　　5. The domain name itself is the problem (if you have your own website)

　　If you are a website owner configuring a domain name for your site, the DNS resolution failure may be a problem at the domain level.

　　Common issues include:

　　Domain Expired: Check your domain registrar's backend to see if the domain status is "active." If it's "ClientHold" or "ServerHold," the DNS resolution is suspended, and you need to renew or complete real-name authentication immediately.

　　Incorrect NS Server Settings: If you purchased a domain from Alibaba Cloud but want to host the DNS resolution with Cloudflare, you need to change the domain's NS server settings in the Alibaba Cloud backend to the two addresses provided by Cloudflare. If you forget to change it, DNS queries won't find the address.

　　Recently Changed NS Server Settings: Changing the NS server settings doesn't take effect instantly; global synchronization can take up to 48 hours. During this period, it's normal for some regions to be able to access the site while others cannot; you just need to wait patiently.

　　If you are a regular internet user and encounter a specific website that you cannot access, it's possible that the website's domain has expired or its DNS has been tampered with. You can use the `nslookup` command to test it. If 8.8.8.8 also cannot be resolved, then it's basically a problem with the domain itself, and not with you.

　　 III. Advanced Troubleshooting (For Those Willing to Try New Troubleshooting)

　　If the above standard steps don't work, then we'll need to get a bit more hardcore. But don't worry, it's just a matter of typing a few more commands.

　　1. Troubleshooting "DNS Client Service Frozen" Issues

　　This is a relatively subtle situation: your computer's network configuration is normal, but it just can't send DNS query packets. Packet capture tools don't even show any DNS requests being sent.

　　Possible Cause: The network driver of some domestic security software (such as 360, Tencent PC Manager) is stuck, causing the DNS Client service to be in a "Stopping" state.

　　Solution:

　　Open PowerShell as administrator and execute:

Get-Service dnscache | Select Status, StartType

　　If you see a Status of "Stopping" or "Paused", it means the service is down. Force restart it:

Stop-Service dnscache -Force
Start-Service dnscache

　　If that doesn't work, you should consider uninstalling recently installed security software and then performing a Winsock reset.

netsh winsock reset
netsh int ip reset
ipconfig /flushdns

　　1. Restart your computer.

　　2. Check if a relay proxy or firewall is blocking traffic.

　　Some corporate or campus networks block or redirect UDP port 53 (the port used by DNS) traffic on their firewalls. In this case, even changing your DNS server won't help because data packets simply can't get through.

　　How to determine this: Use the nslookup command to directly specify a DNS server. If it times out and you don't receive a response, it's likely being blocked.

　　Solution: If you're on a corporate network, contact your network administrator. If it's your own computer, check your Windows firewall settings, or temporarily disable third-party firewall software to test.

　　3. Encrypt DNS with DoH/DoT

　　If your network environment is problematic (e.g., your ISP frequently hijacks DNS to insert ads), or you're always worried about your DNS queries being intercepted, you can try DoH (DNS over HTTPS) or DoT.

　　Edge/Chrome browser settings: Go to Settings → Privacy & Security → Security → Advanced → Turn on "Use secure DNS," then select a service provider, such as Cloudflare or NextDNS. This will encrypt your DNS queries, preventing your ISP from manipulating them.

　　IV. Ultimate Solution: Contact your internet service provider

　　If you've tried all the above methods and the problem persists, it's likely beyond your ability to resolve.

　　Possible scenarios include: widespread DNS server failure in your area, hardware damage to your optical modem or a problem with the optical signal, or your account being suspended due to unpaid bills (although you'd probably already know this).

　　In this case, don't try to fix it yourself; call your broadband provider's customer service directly. Before calling, prepare the following information: when did the problem start, is it affecting all websites or only specific websites, and what actions you've already tried? This will help customer service pinpoint the problem more quickly.

　　Frankly, DNS resolution failure isn't a major issue, but it's not insignificant either. It's not as drastic as a complete internet outage—you can clearly see WeChat messages popping up, but web pages are just blank screens; this kind of "Schrödinger's cat network" is incredibly frustrating. The good news is that in most cases, it really is a cache or configuration issue. Following the steps outlined above, you can usually fix it within 10 minutes.

　　My personal habit is: when a webpage won't open, first refresh the cache (ipconfig/flushdns). If that doesn't work, try changing the IP address to 114.114.114.114. If that still doesn't work, restart the router. These three steps will solve 95% of the problems. The remaining 5% depends on whether you're willing to delve deeper into the issues.