This topic explains common issues related to domain name resolution not taking effect and domain name resolution being effective but unable to access the website.
FAQ
Q: How can I test whether the resolution is effective?
A: To determine whether the resolution is effective, you need to check if the local resolution and authoritative DNS resolution results match your settings. If they match, the resolution is effective. If the local resolution results do not match, we recommend that you wait 10 minutes before testing again (usually because the local DNS cache has not expired). If the authoritative resolution results do not match, you can contact our after-sales support for troubleshooting. For more information, see Methods to test resolution effectiveness.
Q: Why is domain name resolution not taking effect?
A: Common reasons that affect domain name resolution not taking effect:
Newly registered domain names
Expired domain names
Hosted subdomains
Modified resolution records
Modified domain name DNS servers
Not using Cloud DNS servers
Domain name resolution without default line configuration
For more information, see Why is domain name resolution not taking effect?
Q: How to troubleshoot when resolution is not taking effect?
A: Resolution not taking effect mainly refers to DNS query results that do not match your settings in Cloud DNS, or DNS query requests that cannot retrieve the server IP address that the domain name points to. Please refer to the Methods for troubleshooting resolution not taking effect document.
Q: What should I do if DNS resolution does not take effect for a long time?
A: Generally, DNS resolution not taking effect is often caused by the local DNS server cache not being refreshed. It is important to note that the customer's local DNS server (also known as cache DNS server) is not within the control of Cloud DNS service. The cache DNS server caches your DNS resolution records based on the TTL time you set. The resolution effective time for common scenarios is as follows:
Adding resolution records: Takes effect in real-time
Deleting/modifying resolution records: Depends on the expiration time of the TTL for the resolution record in the local DNS cache, generally the default is 10 minutes.
For more information about resolution effective time, see Resolution effective time FAQ document.
Q: What should I do if local DNS resolution is not taking effect?
A: The customer's local DNS server (also known as cache DNS server) is not within the control of Cloud DNS service. The cache DNS server caches your DNS resolution records based on the TTL time you set, so we recommend that you wait for the TTL to expire before testing again. If you do not know how to view or set the TTL cache time, see TTL value setting method.
Q: Why does resolution not take effect in certain regions?
A: Resolution not taking effect in certain regions is generally due to the following two situations:
Local DNS server cache: After modifying the resolution, the resolution effective time depends on the cache refresh time of the local DNS server. If the DNS cache in some regions refreshes quickly, then the resolution takes effect quickly. If the local DNS cache refresh time in some regions is long, the cached information still contains the original resolution results, so these regions will experience resolution not taking effect or inability to access.
Solution: Cloud DNS cannot handle this situation. You can contact your local Internet service provider (ISP) for consultation.
Resolution line settings: If the resolution line does not have a default setting, resolution not taking effect or inability to access may also occur.
Solution: Add a resolution record with Resolution Request Source set to "default" (keep other configurations consistent with the current ineffective resolution record). For specific operations, see Adding resolution records.
Q: Can Cloud DNS help me contact operators to refresh the cache when resolution is not taking effect in some regions?
A: No. Because domain name visitors come from all over the country, local DNS servers across the country will have cached information. Cloud DNS is an authoritative DNS server and cannot solve the cache refresh issues of local DNS servers across the country.
Resolution is effective/unable to access website
Q: Domain name resolution is effective, but the website cannot be opened?
A: Domain name resolution is just one part of website construction. Completing resolution settings does not mean the website can be accessed. When encountering this problem, first test the domain name resolution using the Methods to test resolution effectiveness. If the resolution is normal but the website cannot be accessed, it means the reason for the website not opening is not caused by domain name resolution. We recommend the following:
Check if ports 80 and 443 (when the website uses HTTPS, port 443 needs to be opened) in the security group where the server is located are open. If the server is using Alibaba Cloud ECS server, for security group settings, see Check ECS instance security group rules.
Check if the server service is not started/enabled or if the corresponding port of the service is being listened to. For details, see Check service status and port listening status.
Check if the server's firewall is open and if the corresponding ports are allowed. For details, see Check ECS firewall settings.
If all the above checks are correct, we recommend contacting the technical personnel of the server IP or website space to troubleshoot why the website cannot be accessed.
Q: Resolution is effective, but why can't I ping the domain?
A: If resolution is effective, it means the domain name resolution service is working properly. Generally, being unable to ping is often a network link issue. If your server IP is provided by Alibaba Cloud, you can submit a ticket for server after-sales troubleshooting. If your server IP is not provided by Alibaba Cloud, please contact your server provider for troubleshooting and testing.
Q: The website is sometimes working and sometimes not. Is this due to unstable resolution?
A: We need to clarify whether this is a website opening instability issue, a slow website access issue, or an unstable resolution issue.
Website opening instability and slow website access: These two issues are not within the control of Cloud DNS. The main function of domain name resolution is to resolve the domain name to the website server IP address. So if accessing the domain name can open the webpage, it means the resolution service is working properly. You need to contact your technical personnel to further troubleshoot from multiple aspects such as server configuration, website program, and network environment.
Unstable resolution: When resolving a domain name, the computer first sends a resolution request to the Local DNS. If the Local DNS cache has expired or there is no cache, the Local DNS will send resolution requests to the root DNS, top-level domain DNS, and Cloud DNS (authoritative DNS) in sequence. If the Local DNS is unstable, it may also cause resolution anomalies. So the next time it becomes unstable, please take a screenshot of the Alibaba query tool and submit it to us, submit a ticket.