CloudWatch metrics in Amazon VPC Transit Gateways

Amazon VPC publishes data points to Amazon CloudWatch for your transit gateways and transit gateway attachments. CloudWatch enables you to retrieve statistics about those data points as an ordered set of time series data, known as metrics. Think of a metric as a variable to monitor, and the data points as the values of that variable over time. Each data point has an associated timestamp and an optional unit of measurement.

You can use metrics to verify that your system is performing as expected. For example, you can create a CloudWatch alarm to monitor a specified metric and initiate an action (such as sending a notification to an email address) if the metric goes outside what you consider an acceptable range.

Amazon VPC measures and sends its metrics to CloudWatch in 60-second intervals.

For more information, see the Amazon CloudWatch User Guide.

Transit gateway metrics

The AWS/TransitGateway namespace includes the following metrics.

All metrics are always reported. Their values are dependent on the traffic through the transit gateway. See Transit gateway metric dimensions for the supported dimensions.

Metric	Description
BytesDropCountBlackhole	The number of bytes dropped because they matched a blackhole route. Statistics: The only meaningful statistic is Sum.
BytesDropCountNoRoute	The number of bytes dropped because they did not match a route. Statistics: The only meaningful statistic is Sum.
BytesIn	The number of bytes received by the transit gateway. Statistics: The only meaningful statistic is Sum.
BytesOut	The number of bytes sent from the transit gateway. Statistics: The only meaningful statistic is Sum.
PacketsIn	The number of packets received by the transit gateway. Statistics: The only meaningful statistic is Sum.
PacketsOut	The number of packets sent by the transit gateway. Statistics: The only meaningful statistic is Sum.
PacketDropCountBlackhole	The number of packets dropped because they matched a blackhole route. Statistics: The only meaningful statistic is Sum.
PacketDropCountNoRoute	The number of packets dropped because they did not match a route. Statistics: The only meaningful statistic is Sum.
PacketDropCountTTLExpired	The number of packets dropped because the TTL expired. Statistics: The only meaningful statistic is Sum.

Attachment-level and availability zone metrics

The following metrics are available for transit gateway attachments. All attachment metrics are published to the transit gateway owner's account. Individual attachment metrics are also published to the attachment owner's account. The attachment owner can view only the metrics for their own attachment. For more information on the supported attachment types, see Resource attachments.

Availability zone metrics are available for enabled for availabilty zones (AZs) on transit gateway attachments. Only VPC attachments support per-AZ metrics. All AZ-level metrics are published to the transit gateway owner's account. Individual AZ metrics for an attachment are also published to the attachment owner's account. The attachment owner can view only the per-AZ metrics for their own attachment.

All metrics are always reported. Their values are dependent on the traffic in and/or out of the transit gateway attachment. See Transit gateway metric dimensions for the supported dimensions.

Metric	Description
BytesDropCountBlackhole	The number of bytes dropped because they matched a blackhole route on the transit gateway attachment. Statistics: The only meaningful statistic is Sum.
BytesDropCountNoRoute	The number of bytes dropped because they did not match a route on the transit gateway attachment. Statistics: The only meaningful statistic is Sum.
BytesIn	The number of bytes received by the transit gateway from the attachment. Statistics: The only meaningful statistic is Sum.
BytesOut	The number of bytes sent from the transit gateway to the attachment. Statistics: The only meaningful statistic is Sum.
PacketsIn	The number of packets received by the transit gateway from the attachment. Statistics: The only meaningful statistic is Sum.
PacketsOut	The number of packets sent by the transit gateway to the attachment. Statistics: The only meaningful statistic is Sum.
PacketDropCountBlackhole	The number of packets dropped because they matched a blackhole route on the transit gateway attachment. Statistics: The only meaningful statistic is Sum.
PacketDropCountNoRoute	The number of packets dropped because they did not match a route. Statistics: The only meaningful statistic is Sum.
PacketDropCountTTLExpired	The number of packets dropped because the TTL expired. Statistics: The only meaningful statistic is Sum.

Transit gateway metric dimensions

Filter transit gateway metric data using the following dimensions:

Dimension	Description
TransitGateway	Filters the metric data by transit gateway.
TransitGatewayAttachment	Filters the metric data by transit gateway attachment.
TransitGateway, AvailabilityZone	Filters the metric data by both transit gateway and availability zone.
TransitGatewayAttachment, AvailabilityZone	Filters the metric data by both transit gateway attachment and availability zone.