What

VPC Flow log is to log the traffic within your network

Some Info

Log Level

1. VPC
2. Subnet
3. ENI

Log Info

1. src/dst addr
2. src/dst port
3. action (success/failure)

Log Destination

1. CloudWatch
2. S3 Bucket

Visibility/Dashboard

1. Log Insight (CloudWatch)
2. Athena (S3)

Some Debug Tips

1. Outbound/Inbound failure -> NACL or SG
2. Outbound/Inbound success but return error -> NACL (SG auto allow the return package)