DNS Record Still Not Resolving After Being Recreated

This article explains why a DNS record may continue to return NXDOMAIN or appear unavailable after it has been recreated in UltraDNS.

A common misconception is that recreating a deleted record immediately restores DNS resolution everywhere. 

If recursive DNS servers previously received an NXDOMAIN response while the record was deleted, they may continue to cache that negative response until the negative cache expires.

Symptoms

• A DNS record was deleted and recreated.
• The record exists in UltraDNS and appears correctly configured.
• Some users or DNS resolvers still receive NXDOMAIN responses.
• DNS resolution works from some locations but not others.

Why This Happens

When a DNS resolver receives an NXDOMAIN response from an authoritative name server, it may cache that negative response.

The amount of time that a resolver may cache the negative response is controlled by the domain's SOA Min Cache value.

If a record is deleted and later recreated before the negative cache expires, some recursive DNS servers may continue returning the cached NXDOMAIN response until the cache duration ends.

Verify Whether Negative Caching Is the Cause

1. Confirm the record was deleted and recreated.
   1. Log in to UltraDNS.
   2. Click Audit.
   3. Under Search Audit Records, search for the hostname.
   4. Click Search.
   5. Locate the record with a Change Type of Delete.
   6. Note the time when the record was deleted.
2. Check the domain's SOA Min Cache value.
   1. Click Domains.
   2. Select the domain.
   3. Click the Properties tab.
   4. Locate the value next to Min Cache in the SOA Record section.
   5. Compare the deletion time with the Min Cache value.

For example, if the SOA Min Cache value is 86400, recursive DNS servers may cache the negative response for up to 86,400 seconds after receiving the NXDOMAIN response.

How to Resolve the Issue

1. Clear the cache on recursive DNS servers that provide a cache-clearing option.
2. Wait for negative cache entries to expire on recursive DNS servers that do not provide cache-clearing capabilities.

Expected Outcome

After the negative cache expires, recursive DNS servers will perform a new lookup against the authoritative UltraDNS name servers and receive the current DNS record data.

Important Notes

• Neither UltraDNS nor the domain owner can force third-party recursive DNS servers to immediately remove cached negative responses.
• Once a recursive resolver caches an NXDOMAIN response, it may continue returning that response until the negative cache duration expires.
• If future maintenance requires deleting and recreating records, reducing the SOA Min Cache value before the deletion can reduce the duration of negative caching.
• Changing the SOA Min Cache value after the deletion has already occurred will not affect negative responses that have already been cached by recursive DNS servers.