This article describes the purpose of Secondary DNS and outlines how to configure Secondary DNS at Cloudflare.
Secondary DNS
Secondary DNS allows Cloudflare to act as a Secondary DNS provider to another organization's Master DNS. With Secondary DNS, DNS entries are edited in a system outside of Cloudflare and changes are transferred to Cloudflare's infrastructure. If the current DNS provider does not support Zone Transfer, Cloudflare cannot become a Secondary DNS provider.
Prerequisites
1. Contact your Cloudflare Account team to request Secondary DNS.
2. Update configuration parameters at the primary DNS provider:
Before configuring Cloudflare as your Secondary DNS provider, allow traffic to the Master DNS servers from port 53 and update your Access Control Lists. The Allow Ranges are where Cloudflare's AXFR requests originate and Notify IPs are the IP addresses where you notify Cloudflare's Secondary DNS to initiate a pull of new zone information from your Master DNS servers.
Consult your DNS provider's documentation for instructions on configuring the Master zone.
Allow Range:
- 162.158.64.0/21
- 198.41.144.240/28
- 198.41.150.0/23
- 198.41.152.0/22
- 198.41.246.0/23
- 198.41.250.0/24
- 198.41.252.0/24
- 2a06:98c0:1400::/48
- 2a06:98c0:1401::/48
- 2a06:98c0:3600::/48
- 2a06:98c0:3601::/48
- 2400:cb00:36::/48
- 2606:4700:1101::/64
Notify IPs:
- 172.65.30.82
- 172.65.50.145
- 198.41.246.49
- 2a06:98c0:3600::53
- 2606:4700:60:0:317:26ee:3bdf:5774
- 2606:4700:60:0:35a:4be3:4144:c5ee
For example, to run a BIND server as a primary, add the following statements to your zone file:
allow-transfer {162.158.64.0/21;198.41.144.240/28;198.41.150.0/23;198.41.152.0/22;198.41.246.0/23;198.41.250.0/24;198.41.252.0/24;2a06:98c0:1400::/48;2a06:98c0:1401::/48;2a06:98c0:3600::/48;2a06:98c0:3601::/48;2400:cb00:36::/48;2606:4700:1101::/64;198.41.144.240/28;2a06:98c0:3601::/48;}
also-notify { 198.41.246.49; 2a06:98c0:3600::53;172.65.30.82;172.65.50.145;2606:4700:60:0:317:26ee:3bdf:5774;2606:4700:60:0:35a:4be3:4144:c5ee;}
3. In the Cloudflare Overview app for the domain requiring Secondary DNS:
- Identify the Cloudflare Account ID.
- Identify the Cloudflare Zone ID.
- Note the two Cloudflare Nameservers.
4. Determine the configuration parameters from the Master zone:
- Master IP Address - The IP address that Cloudflare should accept Zone Transfers from.
- Zone transfer type - Will zone transfers be full (AXFR) or incremental (IXFR)?
- (Optional) TSIG Secret - The secret string used to authenticate zone transfers.
- (Optional) TSIG Algorithm - The algorithm used to authenticate zone transfers.
Once the list of prerequisites have been completed, configure the Secondary Zone at Cloudflare.
Configure a Secondary Zone through the Cloudflare API
Secondary DNS can only be configured via the Cloudflare API. Requests can be sent to the API via a command-line utility like cURL or a browser plugin such as Postman.
Refer to the Cloudflare API documentation for full examples on the supported API methods available:
For each POST example provided in the steps below, replace :account_tag with the Account ID identified from the Prerequisites section of this article:
Create a secondary zone through the Create Zone API by setting type to secondary:
curl -X POST "https://api.cloudflare.com/client/v4/zones"
-H "X-Auth-Email: yourname@youremailhere.fyi"
-H "X-Auth-Key: yourapikeyhere"
-H "Content-Type: application/json"
--data '{"name":"examplesecondaryzone.fyi","account":{"id":"accountidhere"},"jump_start":true,"type":"secondary"}'
In the example request below, name and secret must be provided by the primary DNS provider and algo must reflect the correct TSIG algorithm from the Master DNS server. The TSIG name must be lowercase to prevent zone transfer failures.
#POST https://api.cloudflare.com/client/v4/accounts/:account_tag/secondary_dns/tsigs/
{"name": ":tsig_secret_name",
"secret": ":tsig_secret_string",
"algo": "hmac-sha512"} A successful POST request will respond with an id. Include this id when adding a Master.
Multiple Masters can be added via the Cloudflare API.
#POST https://api.cloudflare.com/client/v4/accounts/:account_tag/secondary_dns/masters/
{"ip": ":master_ip",
"port": 53,
"ixfr_enable": true,
"tsig_id": ":tsig_tag"}- :master_ip is the IPv4/IPv6 address of Master nameserver.
- ixfr_enable set to true enables IXFR transfer protocol. The default is AXFR.
- :tsig_tag (optional) is the id provided in the previous step, if configured
A successful POST request will respond with an id for the Master DNS server and must be included when creating a Secondary Zone via the Cloudflare API.
#POST https://api.cloudflare.com/client/v4/zones/:zone_tag/secondary_dns/
{"id": ":zone_tag",
"name": ":zone_name",
"masters": [ ":zone_master_tag" ],
"auto_refresh_seconds": 86400 }- :zone_tag is the Zone ID of the domain configured for Secondary DNS.
- :zone_name is the domain name configured for Secondary DNS.
- :zone_master_tag is the list of Master IDs created in the previous step.
curl -X POST "https://api.cloudflare.com/client/v4/zones/:zone_tag/secondary_dns?force_axfr=true" \ -H "X-Auth-Email: user@example.com" \ -H "X-Auth-Key: yourapikeyhere" \ -H "Content-Type: application/json"
:zone_tag is the Zone ID of the domain configured for Secondary DNS.
See full zone transfer details in the API documentation.
Add Cloudflare's Secondary DNS Nameservers to the existing nameservers specified at your registrar. Review the instructions in the Prerequisites section above to locate the names of your Secondary Nameservers.
Add a TXT record to the primary DNS provider to test transfer to Cloudflare's Secondary DNS servers. Then, verify the TXT record is visible when querying Cloudflare's nameservers. Replace nsNNNN with the correct name of a Cloudflare Secondary DNS servers for the domain:
dig @nsNNN.secondary.cloudflare.com :zone_name txt +short
Configure a Secondary Zone through the Cloudflare Dashboard
1. Log into your Cloudflare Account and click Add site in the Cloudflare dashboard.
2. Enter a site name, choose Secondary DNS, and click Add site.
3. Select the plan type.
4. Add a DNS master via the Cloudflare dashboard:
- Click your profile in the top right and select Account Home.
- Select Configurations from the top navigation.
- Select Secondary DNS from the navigation bar on the left.
- Click Create.
- In the Add a DNS master settings, enter the IP address and Port.
- (Recommended) Configure TSIG by entering the Name, Secret, and Algorithm provided by your primary DNS provider. To prevent zone transfer failures, enter the TSIG name in lowercase.
- Click Continue.
- Confirm the linked DNS masters and add a refresh value in seconds.
- Click Continue.
5. Review the list of transferred records and click Continue.
If a warning message appears, the transfer was unsuccessful. Common reasons for transfer failures include:
- The Access Control List was improperly configured on the master,
- The TSIG was misconfigured, or
- The IP address of the master DNS server was mistyped.
Click Initiate zone transfer after making the necessary changes.
6. Add secondary nameservers to your registrar and click Done, check nameservers.