During an internal DNS query resolution, if no internal record is found within a matching internal zone, Cloudflare will check if the matching internal zone is referencing another internal zone. Successive references can be followed with a maximum of five references in a chain.
- Each internal zone can only reference one other zone.
- The same zone can be referenced by multiple internal zones.
- Public zones cannot be used as reference zones.
- Reference zones do not have to be linked to the same DNS view as the zone referencing them. They may also not be linked to any view at all.
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In the Cloudflare dashboard, go to the Internal DNS page.
Go to Internal DNS ↗ -
Select a zone.
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Within the selected zone, go to Reference zone.
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Select Add reference zone. If your zone already has a reference zone set up, you must first remove it. As explained in the configuration conditions, each internal zone can only reference one other zone at a time.
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Find the zone you want to use as reference and choose Select in the respective row.
Use the Update DNS settings endpoint. In --json, specify the internal_dns object with the parameter reference_zone_id.
In the following example, internal zone A (ID 8a904aeb565c42cfa207d98f6edea2f3) is referencing internal zone B (ID 8e64c6fb4b514f3faf64de81efc11e51).
Required API token permissions
At least one of the following token permissions
is required:
Zone DNS Settings WriteDNS Write
curl "https://api.cloudflare.com/client/v4/zones/8a904aeb565c42cfa207d98f6edea2f3/dns_settings" \
--request PATCH \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--json '{
"internal_dns": {
"reference_zone_id": "8e64c6fb4b514f3faf64de81efc11e51"
}
}'A third zone (C) could also point to zone B as a reference, but zone A cannot add another zone as a reference while also having zone B configured as its reference zone.