Virtual Private Cloud (VPC) networks are global resources. Each VPC network consists of one or more IP address range called subnets. Subnets are regional resources, and have IP address ranges associated with them.
In Google Cloud, the terms subnet and subnetwork are synonymous. They are used interchangeably in the Google Cloud console, Google Cloud CLI commands, and API documentation.
Networks and subnets
A network must have at least one subnet before you can use it. Auto mode VPC networks create subnets in each region automatically. Custom mode VPC networks start with no subnets, giving you full control over subnet creation. You can create more than one subnet per region. For information about the differences between auto mode and custom mode VPC networks, see types of VPC networks.
When you create a resource in Google Cloud, you choose a network and subnet. For resources other than instance templates, you also select a zone or a region. Selecting a zone implicitly selects its parent region. Because subnets are regional objects, the region that you select for a resource determines the subnets that it can use:
When you create an instance, you select a zone for the instance. If you don't select a network for the VM, the default VPC network is used, which has a subnet in every region. If you do select a network for the VM, you must select a network that contains a subnet in the selected zone's parent region.
When you create a managed instance group, you select a zone or region, depending on the group type, and an instance template. The instance template defines which VPC network to use. Therefore, when you create a managed instance group, you must select an instance template with an appropriate configuration; the template must specify a VPC network that has subnets in the selected zone or region. Auto mode VPC networks always have a subnet in every region.
The process of creating a Kubernetes container cluster involves selecting a zone or region (depending on the cluster type), a network, and a subnet. You must select a subnet that is available in the selected zone or region.
Types of subnets
VPC networks support the following subnet types:
IPv4 only (single-stack) subnets, with only IPv4 subnet ranges
IPv4 and IPv6 (dual-stack) subnets, with both IPv4 and IPv6 subnet ranges
A single VPC network can contain any combination of these subnet types.
When you create a subnet, you specify which stack type to use. You can also update an existing IPv4 only subnet to configure it as a dual stack subnet.
Dual-stack subnets are supported on custom mode VPC networks only. Dual-stack subnets are not supported on auto mode VPC networks or legacy networks.
When you create an IPv4 subnet range, you provide the following information:
|Subnet setting||Valid values||Details|
|IPv4 range||A valid range that you choose||Required|
|Secondary IPv4 range||A valid range that you choose||Optional|
When you create an IPv6 subnet range, you provide the following information:
|Subnet setting||Valid values||Details|
|IPv6 access type||
IPv4 subnet ranges
Each subnet has a primary IPv4 address range. The primary internal addresses for the following resources come from the subnet's primary range: VM instances, internal load balancers, and internal protocol forwarding. You can optionally add secondary IP address ranges to a subnet, which are only used by alias IP ranges. However, you can configure alias IP ranges for instances from the primary or secondary range of a subnet.
Your IPv4 subnets don't need to form a predefined contiguous CIDR block, but you can do that if desired. For example, auto mode VPC networks do create subnets that fit within a predefined auto mode IP range.
For more information, see working with subnets.
Valid IPv4 ranges
A subnet's primary and secondary IPv4 address ranges are regional internal IPv4 addresses. The following table describes valid ranges.
|Private IPv4 address ranges|
||Private IP addresses RFC 1918|
||Shared address space RFC 6598|
||IETF protocol assignments RFC 6890|
||Documentation RFC 5737|
||IPv6 to IPv4 relay (deprecated) RFC 7526|
||Benchmark testing RFC 2544|
Some operating systems do not support the use of this range, so verify that your OS supports it before creating subnets that use this range.
|Privately used public IP address ranges|
|Privately used public IPv4 addresses||
Privately used public IPv4 addresses:
When you use these addresses as subnet ranges, Google Cloud does not announce these routes to the internet and does not route traffic from the internet to them.
If you have imported public IP addresses to Google using Bring your own IP (BYOIP), your BYOIP ranges and privately used public IP address ranges in the same VPC network must not overlap.
For VPC Network Peering, subnet routes for public IP addresses are not automatically exchanged. The subnet routes are automatically exported by default, but peer networks must be explicitly configured to import them in order to use them.
IPv4 subnet ranges have the following constraints:
Subnet ranges cannot match, be narrower, or be broader than a restricted range. For example,
22.214.171.124/8is not a valid subnet range because it overlaps with the link-local range
169.254.0.0/16(RFC 3927), which is a restricted range.
Subnet ranges cannot span an RFC range (described in the previous table) and a privately used public IP address range. For example,
126.96.36.199/10is not a valid subnet range because it includes both the
172.16.0.0/12private IP address range and public IP addresses.
Subnet ranges cannot span multiple RFC ranges. For example,
192.0.0.0/8isn't a valid subnet range because it includes both
192.168.0.0/16(from RFC 1918) and
192.0.0.0/24(from RFC 6890). However, you can create two subnets with different primary ranges, one with
192.168.0.0/16and one with
192.0.0.0/24. Or, you could use both of these ranges on the same subnet if you make one of them a secondary range.
Prohibited IPv4 subnet ranges
Prohibited subnet ranges include Google public IP addresses and commonly reserved RFC ranges, as described in the following table. These ranges cannot be used for subnet ranges.
|Public IP addresses for Google APIs and services, including Google Cloud netblocks.||You can find these IP addresses at https://gstatic.com/ipranges/goog.txt.|
|Private Google Access-specific virtual IP addresses|
||Current (local) network RFC 1122|
||Local host RFC 1122|
||Link-local RFC 3927|
||Multicast (Class D) RFC 5771|
||Limited broadcast destination address RFC 8190 and RFC 919|
Reserved IP addresses in IPv4 subnets
Every subnet has four reserved IP addresses in its primary IP range. There are no reserved IP addresses in the secondary IP ranges.
|Reserved IP address||Description||Example|
|Network||First address in the primary IP range for the subnet|
|Default gateway||Second address in the primary IP range for the subnet|
|Second-to-last address||Second-to-last address in the primary IP range for the subnet that is reserved by Google Cloud for potential future use|
|Broadcast||Last address in the primary IP range for the subnet|
Auto mode IPv4 ranges
This table lists the IPv4 ranges for the automatically created subnets in an auto
mode VPC network. IP ranges for these subnets fit inside the
10.128.0.0/9 CIDR block. Auto mode VPC networks are built with
one subnet per region at creation time and automatically receive new subnets in
new regions. Unused portions of
10.128.0.0/9 are reserved for future
Google Cloud use.
|Region||IP range (CIDR)||Default gateway||Usable addresses (inclusive)|
|asia-east1||10.140.0.0/20||10.140.0.1||10.140.0.2 to 10.140.15.253|
|asia-east2||10.170.0.0/20||10.170.0.1||10.170.0.2 to 10.170.15.253|
|asia-northeast1||10.146.0.0/20||10.146.0.1||10.146.0.2 to 10.146.15.253|
|asia-northeast2||10.174.0.0/20||10.174.0.1||10.174.0.2 to 10.174.15.253|
|asia-northeast3||10.178.0.0/20||10.178.0.1||10.178.0.2 to 10.178.15.253|
|asia-south1||10.160.0.0/20||10.160.0.1||10.160.0.2 to 10.160.15.253|
|asia-south2||10.190.0.0/20||10.190.0.1||10.190.0.2 to 10.190.15.253|
|asia-southeast1||10.148.0.0/20||10.148.0.1||10.148.0.2 to 10.148.15.253|
|asia-southeast2||10.184.0.0/20||10.184.0.1||10.184.0.2 to 10.184.15.253|
|australia-southeast1||10.152.0.0/20||10.152.0.1||10.152.0.2 to 10.152.15.253|
|australia-southeast2||10.192.0.0/20||10.192.0.1||10.192.0.2 to 10.192.15.253|
|europe-central2||10.186.0.0/20||10.186.0.1||10.186.0.2 to 10.186.15.253|
|europe-north1||10.166.0.0/20||10.166.0.1||10.166.0.2 to 10.166.15.253|
|europe-west1||10.132.0.0/20||10.132.0.1||10.132.0.2 to 10.132.15.253|
|europe-west2||10.154.0.0/20||10.154.0.1||10.154.0.2 to 10.154.15.253|
|europe-west3||10.156.0.0/20||10.156.0.1||10.156.0.2 to 10.156.15.253|
|europe-west4||10.164.0.0/20||10.164.0.1||10.164.0.2 to 10.164.15.253|
|europe-west6||10.172.0.0/20||10.172.0.1||10.172.0.2 to 10.172.15.253|
|europe-west8||10.198.0.0/20||10.198.0.1||10.198.0.2 to 10.198.0.253|
|europe-west9||10.200.0.0/20||10.200.0.1||10.200.0.2 to 10.200.0.253|
|europe-southwest1||10.204.0.0/20||10.204.0.1||10.204.0.2 to 10.204.15.253|
|northamerica-northeast1||10.162.0.0/20||10.162.0.1||10.162.0.2 to 10.162.15.253|
|northamerica-northeast2||10.188.0.0/20||10.188.0.1||10.188.0.2 to 10.188.15.253|
|southamerica-east1||10.158.0.0/20||10.158.0.1||10.158.0.2 to 10.158.15.253|
|southamerica-west1||10.194.0.0/20||10.194.0.1||10.194.0.2 to 10.194.15.253|
|us-central1||10.128.0.0/20||10.128.0.1||10.128.0.2 to 10.128.15.253|
|us-east1||10.142.0.0/20||10.142.0.1||10.142.0.2 to 10.142.15.253|
|us-east4||10.150.0.0/20||10.150.0.1||10.150.0.2 to 10.150.15.253|
|us-east5||10.202.0.0/20||10.202.0.1||10.202.0.2 to 10.202.15.253|
|us-south1||10.206.0.0/20||10.206.0.1||10.206.0.2 to 10.206.15.253|
|us-west1||10.138.0.0/20||10.138.0.1||10.138.0.2 to 10.138.15.253|
|us-west2||10.168.0.0/20||10.168.0.1||10.168.0.2 to 10.168.15.253|
|us-west3||10.180.0.0/20||10.180.0.1||10.180.0.2 to 10.180.15.253|
|us-west4||10.182.0.0/20||10.182.0.1||10.182.0.2 to 10.182.15.253|
IPv6 subnet ranges
When you enable IPv6 on a subnet in a VPC network, you choose an IPv6 access type for the subnet. The IPv6 access type determines whether the subnet is configured with internal IPv6 addresses or external IPv6 addresses.
Internal IPv6 addresses are used for VM to VM communication within VPC networks. They can only be routed within the scope of VPC networks and cannot be routed to the internet.
External IPv6 addresses can be used for VM to VM communication within VPC networks, and are also routable on the internet.
If a VM interface is connected to a subnet that has an IPv6 subnet range, you can configure IPv6 addresses on the VM. The IPv6 access type of the subnet determines whether the VM is assigned an internal IPv6 address or an external IPv6 address.
IPv6 subnet ranges are regional resources.
Internal and external IPv6 subnet ranges are available in all regions.
IPv6 subnet ranges are automatically assigned
You cannot change the IPv6 access type (internal or external) of a subnet.
You cannot change a dual-stack subnet to single-stack, if the IPv6 access type is internal.
Internal IPv6 specifications
Internal IPv6 ranges use unique local addresses (ULAs).
ULAs for IPv6 are analogous to RFC 1918 addresses for IPv4. ULAs cannot be reached from the internet, and are not publicly routable.
To create subnets with internal IPv6 ranges, you first assign an internal IPv6 range to the VPC network. A
/48IPv6 range is assigned. When you create a subnet with an internal IPv6 range, the subnet's
/64range is assigned from the VPC network's range.
A VPC network's internal IPv6 range is unique within Google Cloud.
You can let Google assign the VPC network internal IPv6 range, or you can select a specific range. If your VPC network connects to networks outside of Google Cloud, you can choose a range that does not overlap with the ranges used in those environments.
The assignment of a VPC network's
/48internal IPv6 range is permanent. You cannot disable it or change it later.
External IPv6 specifications
External IPv6 address ranges use global unicast addresses (GUAs).
External IPv6 addresses can be used for VM to VM communication within VPC networks, and are also routable on the internet. To control egress to and ingress from the internet, configure firewall rules or hierarchical firewall policies. To disable IPv6 routing to the internet completely, delete the IPv6 default route in the VPC network.
External IPv6 addresses are available only in Premium Tier.
Reserving regional external IPv6 addresses is available as a limited Preview feature.
IPv6 range assignment
IPv6 ranges can be assigned to networks, subnets, and virtual machine instances (VMs).
|Resource type||Range size||Details|
To enable internal IPv6 on a subnet, you must first assign an internal IPv6 range on the VPC network.
The IPv6 access type setting controls whether the IPv6 addresses are internal or external.
A subnet can have either internal or external IPv6 addresses, but not both.
When you enable IPv6, the following occurs:
|Virtual machine instance (VM)||
When you enable IPv6 on a VM, the VM is assigned a
You don't configure whether a VM gets internal or external IPv6 addresses. The VM inherits the IPv6 access type from the subnet that it is connected to.
Try it for yourself
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