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 Metric dimensions for transit gateways 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.

Attachment-level 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.

All metrics are always reported. Their values are dependent on the traffic in and/or out of the transit gateway attachment. See Metric dimensions for transit gateways 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 on the transit gateway attachment. Statistics: The only meaningful statistic is Sum.

Metric dimensions for transit gateways

To filter the metrics for your transit gateways, use the following dimensions.

Dimension	Description
TransitGateway	Filters the metric data by transit gateway.
TransitGatewayAttachment	Filters the metric data by transit gateway attachment.