AWS Documentation » AWS CloudFormation » User Guide » Template Reference » AWS Resource Types Reference » AWS::EC2::FlowLog

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AWS::EC2::FlowLog

The AWS::EC2::FlowLog resource creates an Amazon Elastic Compute Cloud (Amazon EC2) flow log that captures IP traffic for a specified network interface, subnet, or VPC. To view the log data, use Amazon CloudWatch Logs (CloudWatch Logs) to help troubleshoot connection issues. For example, you can use a flow log to investigate why certain traffic isn't reaching an instance, which can help you diagnose overly restrictive security group rules. For more information, see VPC Flow Logs in the Amazon VPC User Guide.

Syntax

To declare this entity in your AWS CloudFormation template, use the following syntax:

JSON

{
  "Type" : "AWS::EC2::FlowLog",
  "Properties" : {
    "DeliverLogsPermissionArn" : String,
    "LogGroupName" : String,
    "ResourceId" : String,
    "ResourceType" : String,
    "TrafficType" : String
  }
}

YAML

Type: "AWS::EC2::FlowLog"
Properties:
  DeliverLogsPermissionArn : String
  LogGroupName : String
  ResourceId : String
  ResourceType : String
  TrafficType : String

Properties

DeliverLogsPermissionArn

The Amazon Resource Name (ARN) of an AWS Identity and Access Management (IAM) role that permits Amazon EC2 to publish flow logs to a CloudWatch Logs log group in your account.

Required: Yes

Type: String

Update requires: Replacement

LogGroupName

The name of a new or existing CloudWatch Logs log group where Amazon EC2 publishes your flow logs.

Required: Yes

Type: String

Update requires: Replacement

ResourceId

The ID of the subnet, network interface, or VPC for which you want to create a flow log.

Required: Yes

Type: String

Update requires: Replacement

ResourceType

The type of resource that you specified in the ResourceId property. For example, if you specified a VPC ID for the ResourceId property, specify VPC for this property. For valid values, see the ResourceType parameter for the CreateFlowLogs action in the Amazon EC2 API Reference.

Required: Yes

Type: String

Update requires: Replacement

TrafficType

The type of traffic to log. You can log traffic that the resource accepts or rejects, or all traffic. For valid values, see the TrafficType parameter for the CreateFlowLogs action in the Amazon EC2 API Reference.

Required: Yes

Type: String

Update requires: Replacement

Return Value

Ref

When the logical ID of this resource is provided to the Ref intrinsic function, Ref returns the flow log ID, such as fl-1a23b456.

For more information about using the Ref function, see Ref.

Example

The following example creates a flow log for the VPC called MyVPC and logs all traffic types. Amazon EC2 publishes the logs to the FlowLogsGroup log group.

"MyFlowLog" : {
  "Type" : "AWS::EC2::FlowLog",
  "Properties" : {
    "DeliverLogsPermissionArn" : { "Fn::GetAtt" : ["FlowLogRole", "Arn"] },
    "LogGroupName" : "FlowLogsGroup",
    "ResourceId" : { "Ref" : "MyVPC" },
    "ResourceType" : "VPC",
    "TrafficType" : "ALL"
  }
}