Resolver policies

By default, Gateway sends DNS requests to 1.1.1.1, Cloudflare’s public DNS resolver, for resolution. Enterprise users can instead create Gateway policies to route DNS requests to custom resolvers.

You may use resolver policies if you require access to non-publicly routed domains, such as private network services or internal resources. You may also use resolver policies if you need to access a protected DNS service or want to simplify DNS management for multiple locations.

​​ Resolver connections

Resolver policies support TCP and UDP connections. Custom resolvers can point to the Internet via IPv4 or IPv6, or to a private network service, such as a Magic tunnel. Policies default to port 53. You can change which port your resolver uses by customizing it in your policy.

You can protect your authoritative nameservers from DDoS attacks by enabling DNS Firewall.

​​ Available endpoints

Resolver policies can route queries for resolution from the following DNS endpoints:

• IPv4
• IPv6
• DNS over HTTPS (DoH)
• DNS over TLS (DoT)
• DNS queries generated by Cloudflare Browser Isolation and Clientless Web Isolation
• DNS queries generated by proxy endpoints

Gateway will filter, resolve, and log your queries regardless of endpoint.

​​ Create a resolver policy

1. In Zero Trust Open external link , go to Gateway > Resolver policies.

2. Select Add a policy.

3. Create an expression for your desired traffic. For example, you can resolve a hostname for an internal service:

   Selector	Operator	Value
   Host	in	internal.example.com

4. In Select DNS resolver, choose Configure custom DNS resolvers.

5. Enter the IP addresses of your custom DNS resolver.

6. In Network, choose whether to route queries publicly (to the Internet) or privately (to a private network service).

7. (Optional) Enter a custom port for each IP address.

8. Select Create policy.

Custom resolvers are saved to your account for future use. You can add up to 10 IPv4 and 10 IPv6 addresses to a policy.

When a user’s query matches a resolver policy, Gateway will send the query to your listed resolvers in the following order:

1. Public resolvers
2. Private resolvers behind the default virtual network for your account
3. Private resolvers behind a custom virtual network

Gateway will cache the fastest resolver for use in subsequent queries. Resolver priority is cached on a per user basis for each data center.

For more information on creating a DNS policy, refer to DNS policies.

​​ Selectors

​​ Content Categories

Use this selector to filter domains belonging to specific content categories.

​​ DNS Resolver IP

Use this selector to apply policies to DNS queries that arrived to your Gateway Resolver IP address aligned with a registered DNS location. For most Gateway customers, this is an IPv4 AnyCast address and policies created using this IPv4 address will apply to all DNS locations. However, each DNS location has a dedicated IPv6 address and some Gateway customers have been supplied with a dedicated IPv4 address — these both can be used to apply policies to specific registered DNS locations.

​​ DoH Subdomain

Use this selector to match against DNS queries that arrive via DNS-over-HTTPS (DoH) destined for the DoH endpoint configured for each DNS location. For example, you can use a DNS location with a DoH endpoint of abcdefg.cloudflare-gateway.com by choosing the DoH Subdomain selector and inputting a value of abcdefg.

​​ Domain

Use this selector to match against a domain and all subdomains. For example, you can match example.com and its subdomains, such as www.example.com.

​​ Host

Use this selector to match against only the hostname specified. For example, you can match test.example.com but not example.com or www.test.example.com.

​​ Location

Use this selector to apply policies to a specific Gateway DNS location or set of locations.

​​ Query Record Type

Use this selector to choose the DNS resource record type that you would like to apply policies against. For example, you can match A records for a domain but not MX records.

​​ Security Categories

Use this selector to match domains (and optionally, IP addresses) belonging to specific security categories.

​​ Source Continent

Use this selector to filter based on the continent where the query arrived to Gateway from.

Geolocation is determined from the device’s public IP address (typically assigned by the user’s ISP). To specify a continent, enter its two-letter code into the Value field:

​​ Source Country

Use this selector to filter based on the country where the query arrived to Gateway from.

Geolocation is determined from the device’s public IP address (typically assigned by the user’s ISP). To specify a country, enter its ISO 3166-1 Alpha-2 code Open external link in the Value field.

​​ Source IP

Use this selector to apply policies to the source IP address of DNS queries. For example, this could be the WAN IP address of the stub resolver used by your organization to send queries to Gateway.

​​ Users

Identity-based selectors include:

• SAML Attributes
• User Email
• User Group Emails
• User Group IDs
• User Group Names
• User Name

To use identity-based selectors, enable Gateway with WARP in the Zero Trust WARP client and enroll your user in your organization. For more information, refer to Identity-based policies.

​​ Comparison operators

Comparison operators are the way Gateway matches traffic to a selector. When you choose a Selector in the dashboard policy builder, the Operator dropdown menu will display the available options for that selector.

​​ Value

You can input a single value or use regular expressions to specify a range of values.

Gateway uses Rust to evaluate regular expressions. The Rust implementation is slightly different than regex libraries used elsewhere. For more information, refer to our guide for Wildcards.

For example, if you want to match multiple domains, you could use the pipe symbol (|) as an OR operator. In Gateway, you do not need to use an escape character (\) before the pipe symbol. The following configuration blocks requests to two hosts if either appears in a request header:

To evaluate if your regex matches, you can use Rustexp Open external link .

​​ Logical operators

To evaluate multiple conditions in an expression, select the And logical operator. These expressions can be compared further with the Or logical operator.

The Or operator will only work with conditions in the same expression group. For example, you cannot compare conditions in Traffic with conditions in Identity.