Overview
This article explains a common reason why a delegated subdomain does not resolve from UltraDNS after configuration.
For UltraDNS to answer DNS queries for a delegated subdomain, the parent zone must delegate authority to the UltraDNS name servers using NS records.
Using a CNAME record does not delegate DNS authority and will not allow UltraDNS to answer queries for the subdomain.
Symptoms
- A subdomain has been configured in UltraDNS, but DNS queries do not return the expected records.
- The subdomain was intended to be delegated from another DNS provider to UltraDNS.
- DNS lookups return unexpected results or fail to return records configured in UltraDNS.
- The parent DNS provider shows a CNAME record pointing to UltraDNS name servers.
Why This Happens
DNS delegation and DNS aliasing are different functions.
A CNAME record creates an alias from one hostname to another hostname.
It does not transfer authority for a subdomain to another set of authoritative name servers.
When a subdomain is delegated to UltraDNS, the parent zone must contain NS records for that subdomain.
The NS records tell recursive resolvers which authoritative name servers should answer queries for the delegated namespace.
If a CNAME record is used instead of NS records, DNS resolvers will treat the entry as a hostname alias and will not delegate authority to UltraDNS.
How to Resolve the Issue
- Review the DNS records for the subdomain in the parent zone.
- Confirm whether the subdomain is configured with NS records or a CNAME record.
- If a CNAME record is being used, remove the CNAME record.
- Create the appropriate NS records that delegate the subdomain to the UltraDNS authoritative name servers.
- Verify that the delegated subdomain exists in UltraDNS and contains the required DNS records.
For delegation instructions, see: Delegating a Subdomain to UltraDNS
Expected Outcome
Once the parent zone delegates the subdomain using NS records, DNS queries for the delegated subdomain will be directed to the UltraDNS authoritative name servers, allowing records configured in UltraDNS to resolve correctly.
Important Notes
- CNAME records do not delegate DNS authority.
- Subdomain delegation requires NS records in the parent zone.
- The delegated subdomain must also exist as a zone in UltraDNS.