Logging IP traffic using VPC Flow Logs - Amazon Virtual Private Cloud
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Logging IP traffic using VPC Flow Logs

VPC Flow Logs is a feature that enables you to capture information about the IP traffic going to and from network interfaces in your VPC. Flow log data can be published to the following locations: Amazon CloudWatch Logs, Amazon S3, or Amazon Data Firehose. After you create a flow log, you can retrieve and view the flow log records in the log group, bucket, or delivery stream that you configured.

Flow logs can help you with a number of tasks, such as:

  • Diagnosing overly restrictive security group rules

  • Monitoring the traffic that is reaching your instance

  • Determining the direction of the traffic to and from the network interfaces

Flow log data is collected outside of the path of your network traffic, and therefore does not affect network throughput or latency. You can create or delete flow logs without any risk of impact to network performance.

Note

This section only talks about flow logs for VPCs. For information about flow logs for transit gateways introduced in version 6, see Logging network traffic using Transit Gateway Flow Logs in the Amazon VPC Transit Gateways User Guide.

Pricing

Data ingestion and archival charges for vended logs apply when you publish flow logs. For more information about pricing when publishing vended logs, open Amazon CloudWatch Pricing, select Logs and find Vended Logs.

To track charges from publishing flow logs, you can apply cost allocation tags to your destination resource. Thereafter, your Amazon cost allocation report includes usage and costs aggregated by these tags. You can apply tags that represent business categories (such as cost centers, application names, or owners) to organize your costs. For more information, see the following: