Quickly identify and resolve common DNS resolution issues.
Before you begin
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Use the DNS resolution test methods to verify resolution is working.
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DNS changes take time to propagate. After modifying or deleting a DNS record, wait for the TTL value plus 10 minutes before troubleshooting. How long does it take for a modified or deleted DNS record to take effect?
Identify the issue
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Symptom |
Possible cause |
Details |
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Cannot access from any region |
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1. Abnormal domain name status or incorrect DNS configuration |
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Access issues in some regions |
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DNS record changes do not take effect |
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How long does it take for a modified or deleted DNS record to take effect? |
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DNS server changes do not take effect |
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Cannot send or receive emails |
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DNS resolution is working, but the website is inaccessible |
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1. Abnormal domain status or incorrect DNS configuration
DNS server status
Check: Go to Alibaba Cloud DNS - Public Zone and view the DNS Server IP Address column in the domain name list.
If the status in the DNS Server IP Address column is Normal (indicated by a green check mark), your DNS servers are working correctly.
Symptom: The status is Assigned NS not used, Query NS failed, or Detection Timed Out.
Solution: View DNS server status and handle exceptions.
DNS record issues
Check: Go to Alibaba Cloud DNS - Public Zone, select the domain name to view the list of DNS records.
Symptom: Symptoms include missing or paused DNS records, and incorrect host record or record value settings.
Solution:
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Scenario |
Description |
Solution |
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No relevant DNS records found |
The required DNS record is missing. |
Add the required DNS records based on your business needs. |
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The DNS record is paused |
A DNS record exists but is Paused. |
Enable the DNS record. |
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The host record is set incorrectly |
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Change the host record to the correct value. |
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The record value is set incorrectly |
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Change the record value to the correct value. |
2. Access issues in some regions
Unconfigured Query Source: Default Line
Check: Go to Alibaba Cloud DNS - Public Zone, select the domain name, and then view the list of DNS records.
Symptom: Query Source is set to a specific region or carrier via Smart DNS, but a query does not match the configured line.
Solution:
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Method 1: Change the Query Source to Default.
Use this if you do not need region-specific resolution.
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Method 2: Keep the line-specific configurations and add a Default DNS record.
Add a new DNS record with Query Source set to Default and keep the same settings for all other parameters.
Local DNS cache issues
Check: DNS propagation time depends on the cache refresh interval of local DNS servers. Servers with long cache times may return stale records, causing regional access failures.
Solution: Wait for the local DNS cache to expire. Alibaba Cloud DNS cannot control this. For faster updates, contact your ISP.
3. Email resolution issues
Incorrect record settings
Check: Go to Alibaba Cloud DNS - Public Zone, select the target domain name, and then view the list of DNS records.
Symptom: Symptoms include an incorrect host record, missing DNS records, or duplicate DNS records.
Solution:
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Scenario |
Description |
Solution |
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The host record is incorrectly set |
The configured host records (such as |
Modify the DNS record to match your email provider's requirements. |
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DNS records are missing |
Required records (MX, CNAME, or TXT) specified by your email provider are missing. |
Add the missing records as specified by your email provider. |
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DNS records are duplicated |
Duplicate DNS records (same host record and type) conflict with your email provider's requirements. For example, a new MX record was added before the old one was deleted. |
Delete or pause the duplicate DNS record. |
Propagation delay
New DNS records can take up to 2 hours to propagate. Try again later.
4. Website access issues
Ensure the URL protocol is http, not https
Browsers add the https prefix by default. If you enter demo.example.com, the browser accesses https://demo.example.com, but your site may only support http.
Check: Copy the URL from the browser and verify whether it uses https.
Solution:
Solution 1: Change https to http, then paste the URL into the address bar and try again.
Solution 2: Configure an HTTPS certificate for the website, set the service to listen on port 443, and then access the website by using https.
Website service issues
Website access can fail due to server-side issues such as network problems, firewall rules, or incorrect port configuration. Quickly troubleshoot failures to access websites that are deployed on ECS instances.
FAQ
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Propagation time for DNS records
After modifying or deleting a DNS record, propagation takes up to the record's previous TTL value. For example, a 10-minute TTL means 10 minutes to propagate globally.
Some carriers' local DNS servers enforce longer cache times, delaying propagation up to 48 hours. When modifying a record, keep your service available at both old and new IP addresses to prevent disruption.
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Propagation time for DNS server changes
DNS server change propagation depends on the TTL of the domain's NS record in local DNS caches, which ranges from minutes to 48 hours depending on the TLD.
For example, .com TLD servers cache NS records for up to 48 hours, while .cn TLD servers cache them for 24 hours. A DNS server change can take up to 48 hours to propagate globally.