If you are not seeing expected network traffic information in VPC Flow Logs, what should you check first?

When troubleshooting issues with VPC Flow Logs and unexpected network traffic information, the first thing to check should indeed be the volume of traffic you are filtering for. If the traffic of interest is very low, it may not appear in the logs due to the sampling method employed by VPC Flow Logs. VPC Flow Logs can be set up to sample data, which means that they may only capture a portion of the network traffic, especially when dealing with low-volume situations. Therefore, if there is very little traffic passing through a particular interface or to specific destinations, it is possible that this traffic might fall beneath the threshold that is required for it to be logged, leading to an absence of expected entries in your flow logs.

Recognizing the volume of traffic is crucial, as low-volume data may not be reliably logged, especially compared to higher-volume traffic that is more likely to be captured. Once you confirm that the traffic is indeed of low volume, you can adjust your monitoring and logging strategies appropriately, perhaps by changing the sample rate or looking for different traffic patterns.

The importance of this initial check lies in efficiently narrowing down the cause of the issue before diving into more complex diagnostics. This helps in maintaining effective resource use and time management when working with VPC network