How to troubleshoot DNS faults? Step-by-step processing skills full analysis

in daily network use, we often encounter problems such as webpage failure to load and domain name resolution failure, among which DNS failure is one of the most common incentives. DNS, as the core system of domain name and Internet Protocol Address conversion, will directly affect the stability of network access once there is an abnormality. This article will help you quickly locate and solve various DNS failures through systematic step-by-step skills, from basic detection to deep investigation, so that the network can recover smoothly.

First, do basic DNS connectivity testing?

when network access abnormalities are found, the first step is to confirm whether it is a DNS-level problem through basic testing, which can help us quickly eliminate non-DNS network failures.

1, use the Ping command to detect connectivity

open the command prompt or end point of the system, enter Ping plus the target domain name, such as Ping www.baidu.com. If the prompt of timeout or unable to resolve the domain name is returned, there is a high probability of DNS failure; if the Internet Protocol Address and delay data can be returned normally, it means that the DNS resolution is basically normal, and the problem may be in other links.

2, use the nslookup tool to locate the problem

nslookup is a tool specially used for DNS queries. Enter nslookup plus the target domain name to directly view the resolution results returned by the DNS server. If "server failed" or "domain name not found" is displayed, it means that the DNS server cannot respond to the resolution request normally. Further investigation of the server or local configuration is required.

2, check whether the local DNS configuration is abnormal?

the local DNS configuration error is a common cause of DNS failure, such as DNS server address filling in the wrong, configuration is not effective, etc., this step requires us to carefully check the local DNS related settings.

1 View the local DNS server address

In Windows systems, you can enter ipconfig /all view the DNS server address through the command prompt; in Linux or Mac systems, you can enter cat /etc/resolv.conf through the end point to view. Check whether the displayed address is the correct DNS address provided by the service provider. If there is an error, change it to the official recommended public DNS or service provider DNS in time.

2, check whether the DNS configuration is valid

modify the DNS configuration, you need to refresh the local network configuration to take effect. The Windows system can enter ipconfig /flushdns refresh, the Linux system can restart the network service through systemctl restart network, and the Mac system can disconnect the network settings and reconnect to the network. Then use nslookup to check again to confirm whether the DNS resolution is back to normal.

Check DNS server connectivity and status?

if the local configuration is correct, the DNS fault may be on the server side, and further testing of the connectivity and operating status of the DNS server is required.

1, Ping DNS server address

directly Ping the locally configured DNS server Internet Protocol Address, if the timeout is returned, it indicates that there is a problem with the network connectivity between the local device and the DNS server, which may be a router failure, a network operator line failure, etc., you can contact the network service provider to troubleshoot the line problem.

2, query DNS server running status

through a professional network detection platform, enter the DNS server Internet Protocol Address to inquire about its online status and resolution response speed. If the platform shows that the DNS server is offline or in a timed-out state, it means that the server itself is faulty. You can temporarily switch to the standby DNS server and wait for the official repair before switching back.

4. Clean up the DNS cache to solve the resolution exception?

DNS cache is the system in order to speed up the resolution of temporary resolution records stored, once the cache record expires or error, it will also cause DNS failure, cache cleaning is an effective way to solve such problems.

1, clean the local DNS cache

the cleanup commands for different systems are different. Windows systems enter ipconfig /flushdns at the command prompt, Mac systems enter sudo killall -HUP mDNSResponder at the end point, and Linux systems enter systemctl restart nscd or systemctl restart systemd-resolved. After the cleanup is complete, revisit the target domain name to see if it is back to normal.

2, check the router DNS cache

some routers will also store the DNS cache. If there is still a problem after the local cache is cleaned, you can try to restart the router, which can clean the router's DNS cache and reset the network connection at the same time. Wait 1-2 minutes after restart, let the router re-obtain the DNS configuration, and then test whether the network access is normal.

To sum up, DNS troubleshooting needs to follow a process from basic to deep, first through Ping, nslookup to do basic detection, then check the local DNS configuration, then troubleshoot the DNS server status, and finally clean up the DNS cache. This systematic method can help you quickly locate the root cause of the fault, efficiently solve various DNS-related network problems, and make network access return to stable and smooth.