This article explains why Directional DNS responses in UltraDNS may appear to resolve to the wrong geographic region or alternate between regions. It applies when traffic does not match expected GeoIP behavior, when IP addresses appear to change between regions, or when Directional DNS is used with third-party CDN providers.
Symptoms
- DNS queries resolve to an unexpected geographic region.
- Returned IP addresses appear to alternate between regions such as North America and EMEA.
- Different users in the same physical location receive different DNS answers.
- Directional records that point to CDN hostnames resolve to infrastructure outside the configured region.
- Authority lists are configured correctly, but traffic still appears inconsistent.
Why This Happens
Directional DNS in UltraDNS evaluates the geographic location of the recursive DNS resolver that submits the query, not the end user's physical device. The resolver’s IP address is classified using GeoIP data at query time, and the configured directional rules determine which answer is returned.
Because authoritative DNS servers communicate only with recursive resolvers, UltraDNS does not see the end user's IP address. If different resolvers are used for different queries, each resolver may map to a different geographic region, which results in different DNS responses.
Region changes or “flipping” commonly occur due to one or more of the following:
- Use of multiple recursive resolvers within a network.
- Public DNS services with globally distributed infrastructure.
- Anycast routing that directs queries to different resolver endpoints.
- DNS caching behavior and TTL expiration timing differences.
Impact of CDN and Third-Party Hostnames
When a directional record returns a third-party hostname, such as a CDN endpoint, UltraDNS controls only the initial DNS response. After that hostname is returned, the third-party provider determines the final IP assignment and traffic routing.
UltraDNS is responsible for:
- Correct evaluation of directional rules at query time.
- GeoIP classification of the recursive resolver IP address.
- Returning the configured hostname or IP address.
Third-party providers control:
- Final IP address selection.
- Load balancing behavior.
- Regional traffic routing after DNS resolution.
If traffic ultimately routes outside the expected region after a CDN hostname is returned, that routing behavior occurs outside the UltraDNS authoritative layer.
How to Validate Directional DNS Behavior
To determine whether the behavior originates from UltraDNS configuration or downstream routing, follow these steps:
- Identify the recursive resolver IP address being used for the query.
- Perform a direct query against UltraDNS authoritative name servers to compare responses.
- Confirm whether the directional record returns a direct IP address or a third-party hostname.
- If a hostname is returned, perform an additional lookup of that hostname to determine the final IP assignment.
- Compare results from different recursive resolvers to determine whether GeoIP classification differences are present.
Verification
Directional DNS is functioning as designed when the authoritative response returned by UltraDNS matches the configured regional rules for the resolver IP making the query. If the authoritative response is correct but final routing differs, the behavior is occurring after DNS resolution.
Important Notes
- Directional decisions are made at query time and are based solely on the recursive resolver’s IP address.
- Authority lists do not override resolver GeoIP classification.
- IPv4 and IPv6 resolver addresses may be classified differently.
- DNS caching can cause temporary variation until TTL values expire.