Cloud NAT overview

Cloud NAT provides network address translation (NAT) for outbound traffic to the internet.

Cloud NAT translates addresses for the following resources:

Cloud NAT supports address translation for established inbound response packets only. It doesn't allow unsolicited inbound connections.

By using a Cloud NAT gateway, your Trusted Cloud resources can connect to resources outside of the source VPC network.

Public NAT lets Trusted Cloud resources that don't have external IPv4 addresses communicate with IPv4 destinations on the internet. These VMs use a set of shared external IP addresses to connect to the internet. Cloud NAT doesn't rely on proxy VMs. Instead, a Cloud NAT gateway allocates a set of external IP addresses and source ports to each VM that uses the gateway to create outbound connections to the internet.

Consider a scenario in which you have VM-1 in subnet-1 whose network interface doesn't have an external IP address. However, VM-1 needs to connect to the internet to download updates. To enable connectivity to the internet, you can create a Cloud NAT gateway that is configured to apply to the IP address range of subnet-1. Now, VM-1 can send traffic to the internet by using the internal IP address of subnet-1.

For more information, see Public NAT.

Architecture

Cloud NAT is a distributed, software-defined managed service. It's not based on proxy VMs or appliances. Cloud NAT configures the Andromeda software that powers your Virtual Private Cloud (VPC) network so that it provides source network address translation (source NAT or SNAT) for resources. Cloud NAT also provides destination network address translation (destination NAT or DNAT) for established inbound response packets.

Traditional NAT versus Cloud NAT.
Traditional NAT versus Cloud NAT (click to enlarge).

Benefits

Cloud NAT provides the following benefits:

  • Security

    When using a Cloud NAT gateway for Public NAT, you can reduce the need for individual VMs to each have external IP addresses. Subject to egress firewall rules, VMs without external IP addresses can access destinations on the internet. For example, you might have VMs that only need internet access to download updates or to complete provisioning.

    If you use manual NAT IP address assignment to configure a Cloud NAT gateway for Public NAT, you can confidently share a set of common external source IP addresses with a destination party. For example, a destination service might only allow connections from known external IP addresses.

  • Availability

    Cloud NAT is a distributed, software-defined managed service. It doesn't depend on any VMs in your project or a single physical gateway device. You configure a NAT gateway on a Cloud Router, which provides the control plane for NAT, holding configuration parameters that you specify. Trusted Cloud runs and maintains processes on the physical machines that run your Trusted Cloud VMs.

  • Scalability

    Cloud NAT can be configured to automatically scale the number of NAT IP addresses that it uses, and it supports VMs that belong to managed instance groups, including the groups with autoscaling enabled.

  • Performance

    Cloud NAT does not reduce the network bandwidth per VM. Cloud NAT is implemented by Google's Andromeda software-defined networking. For more information, see Network bandwidth in the Compute Engine documentation.

  • Logging

    For Cloud NAT traffic, you can trace the connections and bandwidth for compliance, debugging, analytics, and accounting purposes.

  • Monitoring

    Cloud NAT exposes key metrics to Cloud Monitoring that give you insight into your fleet's use of NAT gateways. Metrics are sent automatically to Cloud Monitoring. There, you can create custom dashboards, set up alerts, and query metrics.

    Additionally, Network Analyzer publishes Cloud NAT insights. Network Analyzer automatically monitors your Cloud NAT configuration to detect and generate these insights.

Product interactions

For more information about the important interactions between Cloud NAT and other Trusted Cloud products, see Cloud NAT product interactions.

What's next