This page provides an overview of Cloud DNS features and capabilities. Cloud DNS is a high-performance, resilient, global Domain Name System (DNS) service that publishes your domain names to the global DNS in a cost-effective way.
DNS is a hierarchical distributed database that lets you store IP addresses and other data, and look them up by name. Cloud DNS lets you publish your zones and records in DNS without the burden of managing your own DNS servers and software.
Cloud DNS offers both public zones and private managed DNS zones. A public zone is visible to the public internet, while a private zone is visible only from one or more Virtual Private Cloud (VPC) networks that you specify.
For a list of general DNS terminology, see the General DNS overview.
For a list of key terminology on which Cloud DNS is built, see Key terms.
To get started using Cloud DNS, see the Quickstart.
Try it for yourself
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Shared VPC considerations
To use a Cloud DNS managed private zone, Cloud DNS forwarding zone, or Cloud DNS peering zone with Shared VPC, you must create the zone in the host project, and then add one or more Shared VPC networks to the list of authorized networks for that zone.
For more information, see Best practices for Cloud DNS private zones.
DNS forwarding methods
Google Cloud offers inbound and outbound DNS forwarding for private zones. You can configure DNS forwarding by creating a forwarding zone or a Cloud DNS server policy. The two methods are summarized in the following table.
|DNS forwarding||Cloud DNS methods|
Create an inbound server policy to enable an on-premises DNS client or server to send DNS requests to Cloud DNS. The DNS client or server can then resolve records according to a VPC network's name resolution order.
On-premises clients can resolve records in private zones, forwarding zones, and peering zones for which the VPC network has been authorized. On-premises clients use Cloud VPN or Cloud Interconnect to connect to the VPC network.
You can configure VMs in a VPC network to do the following:
You can simultaneously configure inbound and outbound DNS forwarding for a VPC network. Bi-directional forwarding lets VMs in your VPC network resolve records in an on-premises network or in a network hosted by a different cloud provider. This type of forwarding also enables hosts in the on-premises network to resolve records for your Google Cloud resources.
The Cloud DNS control plane uses an algorithm to determine the
responsiveness of a forwarding target. Your outbound forwarded queries might
sometimes result in
SERVFAIL errors. For information about how to work around
this issue, see
Outbound forwarded queries receive SERVFAIL errors.
PTR records for RFC 1918 addresses in private zones
To perform reverse lookups with custom PTR records for RFC 1918 addresses, you must create a Cloud DNS private zone that is at least as specific as one of the following example zones. This is a consequence of the longest suffix matching described in Name resolution order.
Example zones include the following:
17.172.in-addr.arpa., ... through
If you create a Cloud DNS private zone for RFC 1918 addresses, custom PTR records that you create for VMs in that zone are overridden by the PTR records that internal DNS creates automatically. This is because internal DNS PTR records are created in the previous list of more specific zones.
For example, suppose you create a managed private zone for
the following PTR record for a VM whose IP address is
22.214.171.124.in-addr.arpa. -> test.example.domain
PTR queries for
126.96.36.199.in-addr.arpa. are answered by the more specific
10.in-addr.arpa. internal DNS zone. The PTR record in your Cloud DNS
private zone for
test.example.domain is ignored.
To override the automatically created internal DNS PTR
records for VMs, make sure that you create your custom PTR records in a private
zone that is at least as specific as one of the zones presented in this section.
For example, if you create the following PTR record in a private zone for
10.in-addr.arpa., your record overrides the automatically generated
188.8.131.52.in-addr.arpa. -> test.example.domain.
If you only need to override a portion of a network block, you can create
more specific reverse Cloud DNS private zones. For example, a private
5.10.in-addr.arpa. can be used to hold PTR records that override any
internal DNS PTR records that are automatically created
for VMs with IP addresses in the
10.5.0.0/16 address range.
Supported DNS record types
Cloud DNS supports the following types of records.
Address record, which maps host names to their IPv4 address.
IPv6 address record, which maps host names to their IPv6 address.
Certificate Authority (CA) Authorization, which specifies which CAs are allowed to create certificates for a domain.
Canonical name record, which specifies alias names.
Cloud DNS does not support resolving CNAMEs recursively across different managed private zones (CNAME chasing). For details, see CNAME record defined in a private zone not working.
The DNSSEC key from another operator for secure transfer. This record set type can only be added to a DNSSEC-enabled zone in Transfer state.
The DNSSEC key fingerprint for secure delegated zone. This record set type does not activate DNSSEC for a delegated zone unless you enable (and activate) DNSSEC for this zone.
IPsec tunnel gateway data and public keys for IPsec-capable clients to enable opportunistic encryption.
Mail exchange record, which routes requests to mail servers.
Naming authority pointer record, defined by RFC 3403.
Name server record, which delegates a DNS zone to an authoritative server.
Pointer record, which is often used for reverse DNS lookups.
Start of authority record, which specifies authoritative information
about a DNS zone. An
Sender Policy Framework record, a deprecated record type formerly used in email validation systems (use a TXT record instead).
Service locator record, which is used by some voice over IP (VoIP), instant messaging protocols, and other applications.
SSH fingerprint for SSH clients to validate the public keys of SSH servers.
TLS authentication record for TLS clients to validate X.509 server certificates.
Text record, which can contain arbitrary text and can also be used to define machine-readable data, such as security or abuse prevention information.
A TXT record can contain one or more text strings; the maximum length of each individual string is 255 characters. Mail agents and other software agents concatenate multiple strings. Enclose each string in quotation marks.
To work with DNS records, see Managing records.
Wildcard DNS records
Wildcard records are supported for all record types, except for NS records.
Cloud DNS supports managed DNSSEC, protecting your domains from spoofing and cache poisoning attacks. When you use a validating resolver like Google Public DNS, DNSSEC provides strong authentication (but not encryption) of domain lookups. For more information about DNSSEC, see Managing DNSSEC configuration.
Cloud DNS forwarding zones let you configure target name servers for specific private zones. Using a forwarding zone is one way to implement outbound DNS forwarding from your VPC network.
A Cloud DNS forwarding zone is a special type of Cloud DNS private zone. Instead of creating records within the zone, you specify a set of forwarding targets. Each forwarding target is an IP address of a DNS server, located in your VPC network, or in an on-premises network connected to your VPC network by Cloud VPN or Cloud Interconnect.
Forwarding targets and routing methods
Cloud DNS supports three types of targets and offers standard or private methods for routing traffic to them.
|Forwarding target||Description||Standard routing supports||Private routing supports||Source of requests|
|Type 1||An internal IP address of a Google Cloud VM in the same VPC network that is authorized to use the forwarding zone.||Only RFC 1918 IP addresses—traffic always routed through an authorized VPC network.||Any internal IP address, including non-RFC 1918 private IP addresses and privately re-used public IP addresses—traffic always routed through an authorized VPC network.||
|Type 2||An IP address of an on-premises system, connected to the VPC network authorized to query the forwarding zone, using Cloud VPN or Cloud Interconnect.||Only RFC 1918 IP addresses—traffic always routed through an authorized VPC network.||Any internal IP address, including non-RFC 1918 private IP addresses and privately re-used public IP addresses—traffic always routed through an authorized VPC network.||
|Type 3||An external IP address of a DNS name server accessible to the internet or the external IP address of a Google Cloud resource; for example, the external IP address of a VM in another VPC network.||Only internet-routable external IP addresses—traffic always routed to the internet or to the external IP address of a Google Cloud resource.||Private routing isn't supported—make sure that private routing is not selected.||Google Public DNS source ranges|
You can choose one of the two following routing methods when you add the forwarding target to the forwarding zone:
Standard routing: Routes traffic through an authorized VPC network or over the internet based on whether the forwarding target is an RFC 1918 IP address. If the forwarding target is an RFC 1918 IP address, Cloud DNS classifies the target as either a Type 1 or Type 2 target, and routes requests through an authorized VPC network. If the target is not an RFC 1918 IP address, Cloud DNS classifies the target as Type 3, and expects the target to be internet accessible.
Private routing: Always routes traffic through an authorized VPC network, regardless of the target's IP address (RFC 1918 or not). Consequently, only Type 1 and Type 2 targets are supported.
To access a Type 1 or a Type 2 forwarding target, Cloud DNS uses routes in the authorized VPC network where the DNS client is located. These routes define a secure path to the forwarding target:
To send traffic to Type 2 targets, Cloud DNS can use either custom dynamic routes or custom static routes, except for custom static routes with network tags. To reply, Type 2 forwarding targets use routes in your on-premises network.
For additional guidance about network requirements for Type 1 and Type 2 targets, see forwarding target network requirements.
Forwarding target selection order
Cloud DNS lets you configure a list of alternative name servers for an outbound server policy and a list of forwarding targets for a forwarding zone.
In case of multiple forwarding targets, Cloud DNS uses an internal algorithm to select a forwarding target. This algorithm ranks each forwarding target.
To process a request, Cloud DNS first tries a DNS query by contacting the forwarding target with the highest ranking. If that server does not respond, Cloud DNS repeats the request to the next highest ranked forwarding target. If no forwarding targets reply, Cloud DNS synthesizes a SERVFAIL response.
The ranking algorithm is automatic, and the following factors increase the ranking of a forwarding target:
- The higher the number of successful DNS responses processed by the forwarding target. Successful DNS responses include NXDOMAIN responses.
- The lower the latency (round-trip time) for communicating with the forwarding target.
Using forwarding zones
VMs in a VPC network can use a Cloud DNS forwarding zone in the following cases:
- The VPC network has been authorized to use the Cloud DNS forwarding zone. You can authorize multiple VPC networks in the same project to use the forwarding zone.
- The guest operating system of each VM in the VPC network uses
the VM's metadata server
169.254.169.254as its name server.
Overlapping forwarding zones
Because Cloud DNS forwarding zones are a type of Cloud DNS managed private zone, you can create multiple zones that overlap. VMs configured as described earlier resolve a record according to the Name resolution order, using the zone with the longest suffix. For more information, see Overlapping zones.
Caching and forwarding zones
Cloud DNS caches responses for queries sent to Cloud DNS forwarding zones. Cloud DNS maintains a cache of responses from reachable forwarding targets for the shorter of the following time spans:
- 60 seconds
- The duration of the record's time-to-live (TTL)
When all of the forwarding targets for a forwarding zone become unreachable, Cloud DNS maintains its cache of the previously requested records in that zone for the duration of each record's TTL.
When to use peering instead
Cloud DNS cannot use transitive routing to connect to a forwarding target. To illustrate an invalid configuration, consider the following scenario:
You've used Cloud VPN or Cloud Interconnect to connect an on-premises network to a VPC network named
You've used VPC Network Peering to connect VPC network
vpc-net-b. You've configured
vpc-net-ato export custom routes, and
vpc-net-bto import them.
You've created a forwarding zone whose forwarding targets are located in the on-premises network to which
vpc-net-ais connected. You've authorized
vpc-net-bto use that forwarding zone.
Resolving a record in a zone served by the forwarding targets fails in this
scenario, even though there is connectivity from
vpc-net-b to your on-premises
network. To demonstrate this failure, perform the following tests from a
Query the VM's metadata server
169.254.169.254for a record defined in the forwarding zone. This query fails (expectedly) because Cloud DNS does not support transitive routing to forwarding targets. To use a forwarding zone, a VM must be configured to use its metadata server.
Query the forwarding target directly for that same record. Although Cloud DNS does not use this path, this query demonstrates that transitive connectivity succeeds.
You can use a Cloud DNS peering zone to fix this invalid scenario:
- Create a Cloud DNS peering zone authorized for
- Create a forwarding zone authorized for
vpc-net-awhose forwarding targets are on-premises name servers.
You can perform these steps in any order. After completing these steps,
Compute Engine instances in both
vpc-net-b can query
the on-premises forwarding targets.
DNS peering lets you send requests for records that come from one zone's namespace to another VPC network. For example, a SaaS provider can give a SaaS customer access to DNS records it manages.
To provide DNS peering, you must create a Cloud DNS peering zone and configure it to perform DNS lookups in a VPC network where the records for that zone's namespace are available. The VPC network where the DNS peering zone performs lookups is called the DNS producer network.
To use DNS peering, you must authorize a network to use a peering zone. The VPC network authorized to use the peering zone is called the DNS consumer network.
After Google Cloud resources in the DNS consumer network are authorized, they can perform lookups for records in the peering zone's namespace as if they were in the DNS producer network. Lookups for records in the peering zone's namespace follow the DNS producer network's name resolution order.
Therefore, Google Cloud resources in the DNS consumer network can look up records in the zone's namespace from the following sources available in the DNS producer network:
- Cloud DNS managed private zones authorized for use by the DNS producer network.
- Cloud DNS managed forwarding zones authorized for use by the DNS producer network.
- Compute Engine internal DNS names in the DNS producer network.
- An alternative name server, if an outbound server policy has been configured in the DNS producer network.
DNS peering limitations and key points
Keep the following in mind when configuring DNS peering:
- DNS peering is a one-way relationship. It allows Google Cloud resources in the DNS consumer network to look up records in the peering zone's namespace as if the Google Cloud resources were in the DNS producer network.
- The DNS producer and consumer networks must be VPC networks.
- While DNS producer and consumer networks are typically part of the same organization, cross-organizational DNS peering is also supported.
- DNS peering and VPC Network Peering are different services. DNS peering can be used with VPC Network Peering, but VPC Network Peering is not required for DNS peering.
- Transitive DNS peering is supported, but only through a single transitive hop.
In other words, no more than three VPC networks (with the
network in the middle being the transitive hop) can be involved. For example,
you can create a peering zone in
vpc-net-b, and then create a peering zone in
- If you are using DNS peering to target a forwarding zone, the target VPC network with the forwarding zone must contain a VM, a VLAN attachment, or a Cloud VPN tunnel located in the same region as the source VM that uses the DNS peering zone. For details about this limitation, see Forwarding queries from VMs in a consumer VPC network to a producer VPC network not working.
To create a peering zone, you must have the DNS Peer IAM role for the project that contains the DNS producer network.
Two zones overlap with each other when the origin domain name of one zone is either identical to or is a subdomain of the origin of the other zone. For example:
- A zone for
gcp.example.comand another zone for
gcp.example.comoverlap because the domain names are identical.
- A zone for
dev.gcp.example.comand a zone for
dev.gcp.example.comis a subdomain of
Rules for overlapping zones
Cloud DNS enforces the following rules for overlapping zones:
Overlapping public zones are not allowed on the same Cloud DNS name servers. When you create overlapping zones, Cloud DNS attempts to put them on different name servers. If that is not possible, Cloud DNS fails to create the overlapping zone.
A private zone can overlap with any public zone.
Private zones scoped for different VPC networks can overlap with each other. For example, two VPC networks can each have a database VM named
database.gcp.example.comin a zone
gcp.example.com. Queries for
database.gcp.example.comreceive different answers according to the zone records defined in the zone authorized for each VPC network.
Two private zones that have been authorized to be accessible from the same VPC network cannot have identical origins unless one zone is a subdomain of the other. The metadata server uses longest suffix matching to determine which origin to query for records in a given zone.
Query resolution examples
Google Cloud resolves Cloud DNS zones as described in Name resolution order. When determining the zone to query for a given record, Cloud DNS tries to find a zone that matches as much of the requested record as possible (longest suffix matching).
Unless you have specified an alternative name server in an outbound server policy, Google Cloud first attempts to find a record in a private zone (or forwarding zone or peering zone) authorized for your VPC network before it looks for the record in a public zone.
The following examples illustrate the order that the metadata server uses when
querying DNS records. For each of these examples, suppose that you have created
two private zones,
dev.gcp.example.com, and authorized
access to them from the same VPC network. Google Cloud
handles the DNS queries from VMs in a VPC network in the
The metadata server uses public name servers to resolve a record for
myapp.example.com.(note the trailing dot) because there is no private zone for
example.comthat has been authorized for the VPC network. Use
digfrom a Compute Engine VM to query the VM's default name server:
For details, see Query for the DNS name using the metadata server.
The metadata server resolves the record
myapp.gcp.example.comusing the authorized private zone
gcp.example.comis the longest common suffix between the requested record name and available authorized private zones.
NXDOMAINis returned if there's no record for
myapp.gcp.example.comdefined in the
gcp.example.comprivate zone, even if there is a record for
myapp.gcp.example.comdefined in a public zone.
Similarly, queries for
myapp.dev.gcp.example.comare resolved according to records in the authorized private zone
NXDOMAINis returned if there is no record for
dev.gcp.example.comzone, even if there is a record for
myapp.dev.gcp.example.comin another private or public zone.
myapp.prod.gcp.example.comare resolved according to records in the private zone
gcp.example.comis the longest common suffix between the requested DNS record and the available private zones.
Split horizon DNS example
You can use a combination of public and private zones in a split horizon DNS configuration. Private zones enable you to define different responses to a query for the same record when the query originates from a VM within an authorized VPC network. Split horizon DNS is useful whenever you need to provide different records for the same DNS queries depending on the originating VPC network.
Consider the following split horizon example:
- You've created a public zone,
gcp.example.com, and you've configured its registrar to use Cloud DNS name servers.
- You've created a private zone,
gcp.example.com, and you've authorized your VPC network to access this zone.
In the private zone, you've created a single record as shown in the following table.
In the public zone, you've created two records.
The following queries are resolved as described:
- A query for
foo.gcp.example.comfrom a VM in your VPC network returns
- A query for
foo.gcp.example.comfrom the internet returns
- A query for
bar.gcp.example.comfrom a VM in your VPC network returns an
NXDOMAINerror because there’s no record for
bar.gcp.example.comin the private zone
- A query for
bar.gcp.example.comfrom the internet returns
You can manage the users who are allowed to make changes to your DNS records
on the IAM & Admin page in the Google Cloud Console.
For users to be authorized to make changes, they must have either the
Editor role (
roles/editor) or Owner role (
roles/owner) in the Permissions
section of the Cloud Console. The Viewer role (
read-only access to the Cloud DNS records.
These permissions also apply to service accounts that you might use to manage your DNS services.
Access control for managed zones
Users with the project Owner role or Editor role can manage or view the managed zones in the specific project that they are managing.
Users with the DNS Administrator role or DNS Reader role
roles/dns.reader) can manage or view the managed zones
across all the projects that they have access to.
Project Owners, Editors, DNS Administrators, and DNS Readers can view the list of private zones applied to any VPC network in the current project.
Performance and timing
Cloud DNS uses anycast to serve your managed zones from multiple locations around the world for high availability. Requests are automatically routed to the nearest location, reducing latency and improving authoritative name lookup performance for your users.
Propagation of changes
Changes are propagated in two parts. First, the change that you send through the API or command-line tool must be pushed to Cloud DNS's authoritative DNS servers. Second, DNS resolvers must pick up this change when their cache of the records expires.
The time-to-live (TTL) value that you set for your records, which is specified in seconds, controls the DNS resolver's cache. For example, if you set a TTL value of 86400 (the number of seconds in 24 hours), the DNS resolvers are instructed to cache the records for 24 hours. Some DNS resolvers ignore the TTL value or use their own values, which can delay the full propagation of records.
If you are planning for a change to services that requires a narrow window, you might want to change the TTL to a shorter value before making your change. This approach can help reduce the caching window and ensure a quicker change to your new record settings. After the change, you can change the value back to its previous TTL value to reduce load on the DNS resolvers.
- To get started using Cloud DNS, see the Quickstart.
- To register and set up your domain, see the Setting up a domain using Cloud DNS tutorial.
- To learn about API client libraries, see Samples and libraries.
- To find solutions for common issues that you might encounter when using Cloud DNS, see Troubleshooting.