A VPC you create is private: nothing in it reaches the internet or can be reached from it. Internet access takes an Internet Gateway on the VPC, plus one of two ways out for each instance. A Floating IP gives one instance a public IPv4 address in both directions. A NAT gateway gives a whole subnet outbound-only access through one shared address.
The two paths from an instance to the internet:
- Instance with a Floating IP: the Floating IP (1:1 NAT), then the Internet Gateway, then the internet.
- Instance without a Floating IP: the subnet’s route table (
0.0.0.0/0), then a NAT gateway in a public subnet, then the Internet Gateway, then the internet.
Internet traffic is IPv4 only. Instances can’t use IPv6 to or from the internet; see VPC and subnet addressing.
An instance with a Floating IP always uses it, even in a subnet routed through a NAT gateway. An instance with neither has no internet access. On both paths, the subnet’s network ACL and the instance’s security groups must also allow the traffic; see Traffic control.
Key concepts
| Concept | Meaning |
|---|---|
| Internet Gateway | Connects a whole VPC to the internet. A VPC has at most one. Attaching it adds a default route through it to the VPC’s main route table. See Attach and detach an Internet Gateway. |
| Route table | Decides where a subnet’s internet-bound traffic goes: out through the Internet Gateway, through a NAT gateway, or nowhere. Every VPC has a main table, and you can add more. See Route tables. |
| Floating IP | A public IPv4 address you hold in your project and associate with a network interface. The platform translates it 1:1 to the interface’s private address. See Floating IPs. |
| NAT gateway | Shared outbound IPv4 access for instances without a Floating IP. Instances behind it aren’t reachable from the internet. See Give a private subnet internet access with a NAT gateway. |
What you can do
- Attach and detach an Internet Gateway
- Give a private subnet internet access with a NAT gateway
- Allocate, associate and release Floating IPs
Limits and quotas
Internet Gateways, NAT gateways and public IPv4 addresses are limited per organization and project. See Limits.