Logs and metrics

Logging

Cloud NAT logging lets you log NAT connections and errors. When Cloud NAT logging is enabled, one log entry can be generated for each of the following scenarios:

  • When a network connection using NAT is created.
  • When a packet is dropped because no port was available for NAT.

You can choose to log both kinds of events, or only one or the other.

Created logs are sent to Cloud Logging.

Specifications

The following specifications apply to Cloud NAT logging:

  • Cloud NAT logging handles TCP and UDP traffic only.

  • Cloud NAT logging only logs dropped packets if they are egress (outbound) TCP and UDP packets. It does not log dropped incoming packets. For example, if an inbound response to an outbound request is dropped for any reason, no error is logged.

Each VM instance can only generate a certain number of log entries per unit time, proportional to its number of vCPUs. The VM can generate 50-100 log entries per second per vCPU.

  • This rate threshold affects the number of events that can be logged. Even if some events are filtered out, their occurrence counts toward the number of possible log entries. Limiting logs to only errors or only network address translation connections does not necessarily increase the number of viewed log entries. For example, if you choose to log only successful connections, periods of excessive failed connection attempts and NAT errors can still restrict the number of successful connection log entries.

  • Cloud NAT logging does not log every single packet. Even if the VM's rate threshold has not been reached, some conditions can cause events to be omitted from the log. You should rely on the presence of entries in Cloud NAT logging to make informed decisions, but you must not assume that the absence of entries means that an event didn't happen.

Configure logging

To configure Cloud NAT logging, follow these steps.

Enable logging

If logging is enabled, all collected logs are sent to Cloud Logging by default. You can filter these so that only certain logs are sent.

You can also specify these values when you create or edit a NAT gateway. The following directions show how to enable logging for an existing NAT gateway.

Console

  1. In the Google Cloud console, go to the Cloud NAT page.

    Go to Cloud NAT

  2. Click your NAT gateway.

  3. Click Edit.

  4. Click Advanced configurations.

  5. In the Logging section, select one of the following:

    • No logging: disables logging
    • Translation and errors: sends all logs to Logging
    • Translation only: sends a log only when a connection is created; does not log dropped packets
    • Errors only: sends a log when a packet is dropped because no port was available; does not log new connections

  6. Click Save.

gcloud

Use the gcloud compute routers nats update command.

The following commands enable logging for an existing NAT gateway.

In each command, replace the following:

  • NAT_GATEWAY: the name of the NAT gateway
  • ROUTER_NAME: the name of the Cloud Router that hosts the NAT gateway
  • REGION: the region of the Cloud Router

To log network address translation events and errors:

gcloud compute routers nats update NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION \
    --enable-logging

To log only network address translation events:

gcloud compute routers nats update NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION \
    --enable-logging \
    --log-filter=TRANSLATIONS_ONLY

To log only errors:

gcloud compute routers nats update NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION \
    --enable-logging \
    --log-filter=ERRORS_ONLY

Clear log filters

If you have a filter set, you can clear it. Clearing a log filter means that both network address translation events and errors are logged, provided that logging is enabled.

Console

  1. In the Google Cloud console, go to the Cloud NAT page.

    Go to Cloud NAT

  2. Click your NAT gateway.

  3. Click Edit.

  4. Click Advanced configurations.

  5. In the Logging section, select Translation and errors.

  6. Click Save.

gcloud

Use the gcloud compute routers nats update command. The --log-filter=ALL flag in the following command sets the log filter to accept all logs.

gcloud compute routers nats update NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION \
    --log-filter=ALL

Replace the following:

  • NAT_GATEWAY: the name of the NAT gateway
  • ROUTER_NAME: the name of the Cloud Router that hosts the NAT gateway
  • REGION: the region of the Cloud Router

Disable logging

To disable logging, do the following:

Console

  1. In the Google Cloud console, go to the Cloud NAT page.

    Go to Cloud NAT

  2. Click your NAT gateway.

  3. Click Edit.

  4. Click Advanced configurations.

  5. In the Logging section, select No logging.

  6. Click Save.

gcloud

Use the gcloud compute routers nats update command.

gcloud compute routers nats update NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION \
    --no-enable-logging

Replace the following:

  • NAT_GATEWAY: the name of the NAT gateway
  • ROUTER_NAME: the name of the Cloud Router that hosts the NAT gateway
  • REGION: the region of the Cloud Router

Determine logging status

To determine the status for logging, do the following:

Console

  1. In the Google Cloud console, go to the Cloud NAT page.

    Go to Cloud NAT

  2. Click your NAT gateway.

  3. Click Edit.

  4. Click Advanced configurations.

  5. Inspect the selections in the Logging section.

gcloud 

gcloud compute routers nats describe NAT_GATEWAY \
    --router=ROUTER_NAME \
    --region=REGION

Replace the following:

  • NAT_GATEWAY: the name of the NAT gateway
  • ROUTER_NAME: the name of the Cloud Router that hosts the NAT gateway
  • REGION: the region of the Cloud Router

View logs

To view NAT logs, do the following:

Console

  1. In the Google Cloud console, go to the Logs Explorer page.

    Go to Logs Explorer

    • To see all NAT logs, in the Log name menu, select Cloud NAT Gateway.
    • To see logs for only one region, in the Log name menu, select Cloud NAT Gateway, and then slide the cursor right to select a region.
    • To see logs for only one gateway, in the Log name menu, select Cloud NAT Gateway, and then slide the cursor right to select a region. Slide the cursor right again to select a single gateway.

Alternatively, enter the following expression into the query editor:

resource.type="nat_gateway"
logName="projects/{#project_id}/logs/compute.googleapis.com%2Fnat_flows"

gcloud 

gcloud logging read 'resource.type=nat_gateway' \
    --limit=10 \
    --format=json

Where:

  • resource.type=nat_gateway: limits the output to your NAT gateways
  • --limit=10: limits the output to 10 entries; you can input a different value to see more or fewer entries, or omit it entirely to see a continuous scroll of logs
  • --format=json: displays the output in JSON format

For more options, see Reading log entries.

You can configure the export of logs-based metrics for resource logs.

What is logged

Cloud NAT log entries contain information useful for monitoring and debugging your NAT traffic. Log entries contain the following types of information:

  • General information shown in most Google Cloud logs, such as severity, project ID, project number, and timestamp.
  • Specific information related to Cloud NAT. Some log fields contain entries that are themselves multiple fields. These entries and field descriptions are shown in the following tables.

Log fields

Field Value Meaning
connection object(NatIpConnection) 7-tuple describing the source VM IP address and port, NAT source IP address and port, destination IP address and port, and IP address protocol of this connection.
allocation_status enum Indicates whether this connection was successfully allocated or dropped. One of OK or DROPPED.
gateway_identifiers object(NatGateway) The NAT gateway configuration that the connection used.
endpoint object(InstanceDetails) VM instance details. In a Shared VPC configuration, project_id corresponds to the service project.
vpc object(VpcDetails) Virtual Private Cloud (VPC) network details. In a Shared VPC configuration, project_id corresponds to that of the host project.
destination object(DestinationDetails) Details of the destination of the connection.

NatIpConnection field format

Field Type Description
src_ip string Source IP address
src_port int32 Source port
nat_ip string NAT IP address
nat_port int32 NAT assigned port
dest_ip string Destination IP address1
dest_port int32 Destination port
protocol int32 IANA protocol number
1 For NAT64, this field is populated with the destination IPv4-embedded IPv6 address.

NatGateway field format

Field Type Description
gateway_name string Name of the NAT gateway
router_name string Cloud Router associated with the NAT gateway
region string Region of the Cloud Router

InstanceDetails field format

Field Type Description
project_id string ID of the project containing the VM
vm_name string Instance name of the VM
region string Region of the VM
zone string Zone of the VM

VpcDetails field format

Field Type Description
project_id string ID of the project containing the network
vpc_name string Network on which the VM is operating
subnetwork_name string Subnet on which the VM is operating

DestinationDetails field format

Field Type Description
geo_location object(GeographicDetails) If the destination of the connection was external to Google Cloud, this field is populated with available location metadata.
instance object(InstanceDetails) If the destination of the connection is an instance within the same project as the source, this field is populated with VM instance details.
vpc object(VpcDetails) If the destination of the connection is within the same project as the source, this field is populated with the destination VPC network details. If the destination is a cross-project VPC network, then this field will display a blank.

GeographicDetails field format

Field Type Description
continent string Continent for external endpoints
country string Country for external endpoints
region string Region for external endpoints
city string City for external endpoints
asn string The autonomous system number (ASN) of the external network to which this endpoint belongs.

Examples

Example 1: NAT-ed TCP connection record from a VM instance in a Shared VPC network going to an external server in France.

{
insertId: "1the8juf6vab1t"
jsonPayload: {
       connection: {
            Src_ip: "10.0.0.1"
            Src_port: 45047
            Nat_ip: "203.0.113.17"
            Nat_port: 34889
            dest_ip : "198.51.100.142"
            Dest_port: 80
            Protocol: "tcp"
       }
       allocation_status: "OK"
       Gateway_identifiers: {
             Gateway_name: "my-nat-1"
             router_name: "my-router-1"
             Region: "europe-west1"
       }
       Endpoint: {
             Project_id: "service-project-1"
             Vm_name: "vm-1"
             Region: "europe-west1"
             Zone: "europe-west1-b"
       }
       Vpc: {
             Project_id: "host-project"
             Vpc_name: "network-1"
             Subnetwork_name: "subnetwork-1"
       }
       Destination: {
             Geo_location: {
                   Continent: "Europe"
                   Country: "France"
                   Region: "Nouvelle-Aquitaine"
                   City: "Bordeaux"
             }
       }
}
logName: "projects/host-project/logs/compute.googleapis.com%2Fnat_flows"
receiveTimestamp: "2018-06-28T10:46:08.123456789Z"
resource: {
      labels: {
            region: "europe-west1-d"
            project_id: "host-project"
            router_id: "987654321123456"
            gateway_name: "my-nat-1"
      }
      type: "nat_gateway"
}
labels: {
      nat.googleapis.com/instance_name: "vm-1"
      nat.googleapis.com/instance_zone: "europe-west1-b"
      nat.googleapis.com/nat_ip: "203.0.113.17"
      nat.googleapis.com/network_name: "network-1"
      nat.googleapis.com/router_name: "my-router-1"
      nat.googleapis.com/subnetwork_name: "subnetwork-1"
}
timestamp: "2018-06-28T10:46:00.602240572Z"
}

Example 2: Record for a packet dropped because there were no available ports. Sending VM was trying to reach the external IP address of another VM in the same project.

{
insertId: "1the8juf6vab1l"
jsonPayload: {
       connection: {
            Src_ip: "10.0.128.1"
            Src_port: 45047
            dest_ip : "192.0.2.87"
            Dest_port: 80
            Protocol: "tcp"
       }
       allocation_status: "DROPPED"
       Gateway_identifiers: {
             Gateway_name: "my-nat-2"
             Cloud_router: "my-router-1"
             Region: "europe-west1"
       }
       Endpoint: {
             Project_id: "service-project-1"
             Vm_name: "vm-1"
             Region: "europe-west1"
             Zone: "europe-west1-b"
       }
       Vpc: {
             Project_id: "host-project"
             Vpc_name: "network-1"
             Subnetwork_name: "subnetwork-1"
       }
       Destination: {
             Instance: {
                   Project_id: "service-project-1"
                   Vm_name: "vm-2"
                   Region: "asia-east1"
                   Zone: "asia-east1-b"
             }
       }
}
logName: "projects/host-project/logs/compute.googleapis.com%2Fnat_flows"
receiveTimestamp: "2018-06-28T10:46:09.123456789Z"
resource: {
       labels: {
              region: "europe-west1-d"
              project_id: "host-project"
              router_id: "987654321123456"
              gateway_name: "my-nat-2"
       }
       type: "nat_gateway"
}
timestamp: "2018-06-28T10:46:01.602240572Z"
}

Pricing for Cloud NAT logging

See Logging pricing.

Monitoring

Cloud NAT exposes key metrics to Cloud Monitoring that give you insights into your fleet's usage of NAT gateways.

Metrics are sent automatically to Cloud Monitoring. There, you can create custom dashboards, set up alerts, and query the metrics.

Following are the required Identity and Access Management (IAM) roles:

  • For Shared VPC users with VMs and NAT gateways defined in different projects, access to the VM level metrics requires the roles/monitoring.viewer IAM role for the project of each VM.

  • For the NAT gateway resource, access to the gateway metrics requires the roles/monitoring.viewer IAM role for the project that contains the gateway.

View predefined dashboards

Cloud NAT provides a set of predefined dashboards that display activity across your gateway:

  • Open connections
  • Egress data processed by NAT (rate)
  • Ingress data processed by NAT (rate)
  • Port usage
  • NAT allocation errors
  • Dropped sent packets rate
  • Dropped received packets rate

To view predefined dashboards from the details page of a particular gateway, follow these steps:

Console

  1. In the Google Cloud console, go to the Cloud NAT page.

    Go to Cloud NAT

  2. Click an existing gateway.

  3. Click the Monitoring tab.

  4. Scroll to see all the dashboards. You can change the view from 1 hour to 30 days by using the control at the top of the page. Hovering over a point on the graph gives you details for that specific time.

Define custom dashboards

To create a custom dashboard to view VM instance metrics or NAT gateway metrics, follow these steps:

Console

  1. In the Google Cloud console, go to the  Dashboards page:

    Go to Dashboards

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Click Create dashboard
  3. Optional: Update the dashboard title with a descriptive name for your dashboard.
  4. Click Add Widget and then select Metric.
  5. Expand the Metric menu, enter Cloud NAT Gateway or VM Instance in the filter bar, and then use the submenus to select a specific resource type and metric:
    1. In the Active resources menu, select Cloud NAT Gateway or VM Instance.
    2. In the Active metric categories menu, select Nat.
    3. In the Active metrics menu, select the metric that you want to view.
    4. Click Apply.
  6. Combine time series:
    • To display every time series, in the Aggregation element, ensure the first menu is set to Unaggregated and the second menu is set to None.

    • To combine time series, in the Aggregation element, use the first menu to select a function and the second menu to select the labels. If the second menu is set to None, then the chart displays one time series.

      For example, to display the average value of time series after grouping by zone, set the first menu to Mean and the second to zone.

    For information about combining time series, see Choose how to display charted data.

  7. For each additional widget that you want to add to your dashboard, click Add widget, complete the dialog, and then select Apply.

    For more information about adding widgets, see the following pages:

Define alerting policies

To create a metrics-based alerting policy, follow these steps:

Console

You can create alerting policies to monitor the values of metrics and to notify you when those metrics violate a condition.

  1. In the Google Cloud console, go to the  Alerting page:

    Go to Alerting

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. If you haven't created your notification channels and if you want to be notified, then click Edit Notification Channels and add your notification channels. Return to the Alerting page after you add your channels.
  3. From the Alerting page, select Create policy.
  4. To select the metric, expand the Select a metric menu and then do the following:
    1. To limit the menu to relevant entries, enter Cloud NAT gateway or VM Instance into the filter bar. If there are no results after you filter the menu, then disable the Show only active resources & metrics toggle.
    2. For the Resource type, select Cloud NAT gateway or VM Instance.
    3. Select a Metric category and a Metric, and then select Apply.
  5. Click Next.
  6. The settings in the Configure alert trigger page determine when the alert is triggered. Select a condition type and, if necessary, specify a threshold. For more information, see Create metric-threshold alerting policies.
  7. Click Next.
  8. Optional: To add notifications to your alerting policy, click Notification channels. In the dialog, select one or more notification channels from the menu, and then click OK.
  9. Optional: Update the Incident autoclose duration. This field determines when Monitoring closes incidents in the absence of metric data.
  10. Optional: Click Documentation, and then add any information that you want included in a notification message.
  11. Click Alert name and enter a name for the alerting policy.
  12. Click Create Policy.
For more information, see Alerting overview.

Metric reporting frequency and retention

Metrics for Cloud NAT are batched and exported to Monitoring every one (1) minute. Monitoring data is retained for six (6) weeks. The dashboard provides data analysis in default intervals of 1H (one hour), 6H (six hours), 1D (one day), 1W (one week), and 6W (six weeks). You can manually request analysis in any interval from 6W to 1 minute.

VM instance metrics

The "metric type" strings in this table must be prefixed with compute.googleapis.com/. That prefix has been omitted from the entries in the table.

Metric type Launch stage
Display name
Kind, Type, Unit
Monitored resources		 Description
Labels
nat/allocated_ports GA
Allocated ports
GAUGE, INT64, {port}
gce_instance 		Number of ports allocated to a VM by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
nat_ip: The NAT IP allocated to the NAT gateway.
nat/closed_connections_count GA
Closed connections count
DELTA, INT64, {connection}
gce_instance 		Count of connections closed over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/dropped_received_packets_count GA
Received packets dropped count
DELTA, INT64, {packet}
gce_instance 		Count of received packets dropped by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/dropped_sent_packets_count GA
Sent packets dropped count
DELTA, INT64, {packet}
gce_instance 		Count of sent packets dropped by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
reason: The reason for the packet drop. Possible values are OUT_OF_RESOURCES, ENDPOINT_INDEPENDENCE_CONFLICT.
nat/new_connections_count GA
New connections count
DELTA, INT64, {connection}
gce_instance 		Count of new connections created over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/open_connections GA
Open connections
GAUGE, INT64, {connection}
gce_instance 		Number of connections open on the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/port_usage GA
Port usage
GAUGE, INT64, {port}
gce_instance 		Maximum number of connections from a VM to a single destination endpoint (IP:port). Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/received_bytes_count GA
Received bytes count
DELTA, INT64, By
gce_instance 		Count of bytes received (destination -> source) through the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/received_packets_count GA
Received packets count
DELTA, INT64, {packet}
gce_instance 		Count of packets received (destination -> source) through the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/sent_bytes_count GA
Sent bytes count
DELTA, INT64, By
gce_instance 		Count of bytes sent (source -> destination) over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/sent_packets_count GA
Sent packets count
DELTA, INT64, {packet}
gce_instance 		Count of packets sent (source -> destination) over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 165 seconds.
nat_project_number: The project number to which the NAT gateway belongs.
router_id: The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name: The name of the NAT gateway.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.

VM instance filtering dimensions

label_key Type Description
project_id STRING The project ID of the VM instance.
instance_id STRING The ID of the VM instance.
zone STRING The zone of the VM instance.
nat_project_number STRING The project number to which the NAT gateway belongs.
router_id STRING The Cloud Router ID to which the NAT gateway belongs.
nat_gateway_name STRING The name of the NAT gateway.
nat_ip STRING The NAT IP address allocated to the NAT gateway. Valid for metrics allocated_ports.
ip_protocol STRING The protocol of the connection. Can be TCP, UDP or ICMP. Valid for all metrics except allocated_ports.
reason STRING

The reason for the packet drop. Possible values are:

  • OUT_OF_RESOURCES, if Cloud NAT runs out of NAT IP addresses or ports.
  • ENDPOINT_INDEPENDENCE_CONFLICT, when an endpoint independent conflict arises.

Valid for metrics dropped_sent_packets_count.

NAT gateway metrics

The "metric type" strings in this table must be prefixed with router.googleapis.com/. That prefix has been omitted from the entries in the table.

Metric type Launch stage
Display name
Kind, Type, Unit
Monitored resources		 Description
Labels
nat/allocated_ports GA
Allocated ports
GAUGE, INT64, {port}
nat_gateway 		Number of ports allocated to all VMs by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
nat_ip: NAT IP of the ports.
nat/closed_connections_count GA
Closed connections count
DELTA, INT64, {connection}
nat_gateway 		Count of connections closed over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/dropped_received_packets_count GA
Received packets dropped count
DELTA, INT64, {packet}
nat_gateway 		Count of received packets dropped by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/dropped_sent_packets_count GA
Sent packets dropped count
DELTA, INT64, {packet}
nat_gateway 		Count of sent packets dropped by the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
reason: The reason for the packet drop. Possible values are OUT_OF_RESOURCES, ENDPOINT_INDEPENDENCE_CONFLICT.
nat/nat_allocation_failed GA
NAT allocation failed
GAUGE, BOOL, 
nat_gateway 		Indicates if there is a failure in allocating NAT IPs to any VM in the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 120 seconds.
nat/new_connections_count GA
New connections count
DELTA, INT64, {connection}
nat_gateway 		Count of new connections created over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/open_connections GA
Open connections
GAUGE, INT64, {connection}
nat_gateway 		Number of connections open on the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/port_usage GA
Port usage
GAUGE, INT64, {port}
nat_gateway 		Maximum number of connections from a VM to a single destination endpoint (IP:port). Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/received_bytes_count GA
Received bytes count
DELTA, INT64, By
nat_gateway 		Count of bytes received (destination -> source) through the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/received_packets_count GA
Received packets count
DELTA, INT64, {packet}
nat_gateway 		Count of packets received (destination -> source) through the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/sent_bytes_count GA
Sent bytes count
DELTA, INT64, By
nat_gateway 		Count of bytes sent (source -> destination) over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.
nat/sent_packets_count GA
Sent packets count
DELTA, INT64, {packet}
nat_gateway 		Count of packets sent (source -> destination) over the NAT gateway. Sampled every 60 seconds. After sampling, data isn't visible for up to 225 seconds.
ip_protocol: The protocol of the connection. Can be TCP, UDP or ICMP.

Gateway filtering dimensions

label_key Type Description
project_id STRING The project ID of the gateway.
region STRING The region of the gateway.
router_id STRING The Cloud Router ID to which the NAT gateway belongs.
gateway_name STRING The name of the NAT gateway.
ip_protocol STRING The protocol of the connection. Can be TCP, UDP or ICMP. Valid for all metrics except allocated_ports.
nat_ip STRING The NAT IP address allocated to the NAT gateway. Valid for metrics allocated_ports.
reason STRING

The reason for the packet drop. Possible values are:

  • OUT_OF_RESOURCES, if Cloud NAT runs out of NAT IP addresses or ports.
  • ENDPOINT_INDEPENDENCE_CONFLICT, when an endpoint independent conflict arises.

Valid for metrics dropped_sent_packets_count.

Query metrics using the Monitoring API

You can construct arbitrary queries over the Cloud NAT metrics by using the Monitoring API's v3 projects.timeSeries.list request.

API example

Getting allocated ports of a VM, with 1m aggregates, timeSeries.list parameters:

  • name: projects/PROJECT_ID
  • Filter: resource.type = "gce_instance" AND metric.name="compute.googleapis.com/nat/allocated_ports" AND metric.labels.nat_gateway_name="nat-1-237227-1569344091-5"
  • interval.start_time: 2019-09-24T16:58:53Z
  • interval.end_time: 2019-09-24T16:58:53Z
  • aggregation.alignmentPeriod: 60s
  • aggregation.crossSeriesReducer: REDUCE_SUM
  • aggregation.perSeriesAligner: ALIGN_SUM
"timeSeries": [
    {
      "resource": {
        "labels": {
          "instance_id": "1406292833167995938",
          "project_id": "PROJECT_ID",
          "zone": "us-west1-c"
        },
        "type": "gce_instance"
      },
      "metric": {
        "labels": {
          "nat_ip": "70.32.157.11",
          "nat_gateway_name": "nat-1-237227-1569344091-5",
          "nat_project_number": "PROJECT_NUMBER",
          "router_id": "1380055590921303155"
        },
        "type": "compute.googleapis.com/nat/allocated_ports"
      },
      "metricKind": "GAUGE",
      "points": [
        {
          "interval": {
            "endTime": "2019-09-24T16:58:53.699Z",
            "startTime": "2019-09-24T16:58:53.699Z"
          },
          "value": {
            "int64Value": "64"
          }
        }
      ],
      "valueType": "INT64"
    },

Pricing for Cloud NAT monitoring

There is no cost for Cloud NAT monitoring.

What's next