# Allocate a network interface for an Amazon ECS task The task networking features that are provided by the `awsvpc` network mode give Amazon ECS tasks the same networking properties as Amazon EC2 instances. Using the `awsvpc` network mode simplifies container networking, because you have more control over how your applications communicate with each other and other services within your VPCs. The `awsvpc` network mode also provides greater security for your containers by allowing you to use security groups and network monitoring tools at a more granular level within your tasks. You can also use other Amazon EC2 networking features such as VPC Flow Logs to monitor traffic to and from your tasks. Additionally, containers that belong to the same task can communicate over the `localhost` interface. The task elastic network interface (ENI) is a fully managed feature of Amazon ECS. Amazon ECS creates the ENI and attaches it to the host Amazon EC2 instance with the specified security group. The task sends and receives network traffic over the ENI in the same way that Amazon EC2 instances do with their primary network interfaces. Each task ENI is assigned a private IPv4 address by default. If your VPC is enabled for dual-stack mode and you use a subnet with an IPv6 CIDR block, the task ENI will also receive an IPv6 address. Each task can only have one ENI. These ENIs are visible in the Amazon EC2 console for your account. Your account can't detach or modify the ENIs. This is to prevent accidental deletion of an ENI that is associated with a running task. You can view the ENI attachment information for tasks in the Amazon ECS console or with the [DescribeTasks](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_DescribeTasks.html) API operation. When the task stops or if the service is scaled down, the task ENI is detached and deleted. When you need increased ENI density, use the `awsvpcTrunking` account setting. Amazon ECS also creates and attaches a "trunk" network interface for your container instance. The trunk network is fully managed by Amazon ECS. The trunk ENI is deleted when you either terminate or deregister your container instance from the Amazon ECS cluster. For more information about the `awsvpcTrunking` account setting, see [Prerequisites](container-instance-eni.md#eni-trunking-launching). You specify `awsvpc` in the `networkMode` parameter of the task definition. For more information, see [Network mode](task_definition_parameters.md#network_mode). Then, when you run a task or create a service, use the `networkConfiguration` parameter that includes one or more subnets to place your tasks in and one or more security groups to attach to an ENI. For more information, see [Network configuration](service_definition_parameters.md#sd-networkconfiguration). The tasks are placed on compatible Amazon EC2 instances in the same Availability Zones as those subnets, and the specified security groups are associated with the ENI that's provisioned for the task. ## Linux considerations Consider the following when using the Linux operating system. + If you use a p5.48xlarge instance in `awsvpc` mode, you can't run more than 1 task on the instance. + Tasks and services that use the `awsvpc` network mode require the Amazon ECS service-linked role to provide Amazon ECS with the permissions to make calls to other AWS services on your behalf. This role is created for you automatically when you create a cluster or if you create or update a service, in the AWS Management Console. For more information, see [Using service-linked roles for Amazon ECS](using-service-linked-roles.md). You can also create the service-linked role with the following AWS CLI command: ``` aws iam [create-service-linked-role](https://docs.aws.amazon.com/cli/latest/reference/iam/create-service-linked-role.html) --aws-service-name ecs.amazonaws.com ``` + Your Amazon EC2 Linux instance requires version `1.15.0` or later of the container agent to run tasks that use the `awsvpc` network mode. If you're using an Amazon ECS-optimized AMI, your instance needs at least version `1.15.0-4` of the `ecs-init` package as well. + Amazon ECS populates the hostname of the task with an Amazon-provided (internal) DNS hostname when both the `enableDnsHostnames` and `enableDnsSupport` options are enabled on your VPC. If these options aren't enabled, the DNS hostname of the task is set to a random hostname. For more information about the DNS settings for a VPC, see [Using DNS with Your VPC](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-dns.html) in the *Amazon VPC User Guide*. + Each Amazon ECS task that uses the `awsvpc` network mode receives its own elastic network interface (ENI), which is attached to the Amazon EC2 instance that hosts it. There's a default quota for the number of network interfaces that can be attached to an Amazon EC2 Linux instance. The primary network interface counts as one toward that quota. For example, by default, a `c5.large` instance might have only up to three ENIs that can be attached to it. The primary network interface for the instance counts as one. You can attach an additional two ENIs to the instance. Because each task that uses the `awsvpc` network mode requires an ENI, you can typically only run two such tasks on this instance type. For more information about the default ENI limits for each instance type, see [IP addresses per network interface per instance type](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html#AvailableIpPerENI) in the *Amazon EC2 User Guide*. + Amazon ECS supports the launch of Amazon EC2 Linux instances that use supported instance types with increased ENI density. When you opt in to the `awsvpcTrunking` account setting and register Amazon EC2 Linux instances that use these instance types to your cluster, these instances have higher ENI quota. Using these instances with this higher quota means that you can place more tasks on each Amazon EC2 Linux instance. To use the increased ENI density with the trunking feature, your Amazon EC2 instance must use version `1.28.1` or later of the container agent. If you're using an Amazon ECS-optimized AMI, your instance also requires at least version `1.28.1-2` of the `ecs-init` package. For more information about opting in to the `awsvpcTrunking` account setting, see [Access Amazon ECS features with account settings](ecs-account-settings.md). For more information about ENI trunking, see [Increasing Amazon ECS Linux container instance network interfaces](container-instance-eni.md). + When hosting tasks that use the `awsvpc` network mode on Amazon EC2 Linux instances, your task ENIs aren't given public IP addresses. To access the internet, tasks must be launched in a private subnet that's configured to use a NAT gateway. For more information, see [NAT gateways](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html) in the *Amazon VPC User Guide*. Inbound network access must be from within a VPC that uses the private IP address or routed through a load balancer from within the VPC. Tasks that are launched within public subnets do not have access to the internet. + Amazon ECS recognizes only the ENIs that it attaches to your Amazon EC2 Linux instances. If you manually attached ENIs to your instances, Amazon ECS might attempt to add a task to an instance that doesn't have enough network adapters. This can result in the task timing out and moving to a deprovisioning status and then a stopped status. We recommend that you don't attach ENIs to your instances manually. + Amazon EC2 Linux instances must be registered with the `ecs.capability.task-eni` capability to be considered for placement of tasks with the `awsvpc` network mode. Instances running version `1.15.0-4` or later of `ecs-init` are registered with this attribute automatically. + The ENIs that are created and attached to your Amazon EC2 Linux instances cannot be detached manually or modified by your account. This is to prevent the accidental deletion of an ENI that is associated with a running task. To release the ENIs for a task, stop the task. + There is a limit of 16 subnets and 5 security groups that are able to be specified in the `awsVpcConfiguration` when running a task or creating a service that uses the `awsvpc` network mode. For more information, see [AwsVpcConfiguration](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_AwsVpcConfiguration.html) in the *Amazon Elastic Container Service API Reference*. + When a task is started with the `awsvpc` network mode, the Amazon ECS container agent creates an additional `pause` container for each task before starting the containers in the task definition. It then configures the network namespace of the `pause` container by running the [amazon-ecs-cni-plugins ](https://github.com/aws/amazon-ecs-cni-plugins) CNI plugins. The agent then starts the rest of the containers in the task so that they share the network stack of the `pause` container. This means that all containers in a task are addressable by the IP addresses of the ENI, and they can communicate with each other over the `localhost` interface. + Services with tasks that use the `awsvpc` network mode only support Application Load Balancer and Network Load Balancer. When you create any target groups for these services, you must choose `ip` as the target type. Do not use `instance`. This is because tasks that use the `awsvpc` network mode are associated with an ENI, not with an Amazon EC2 Linux instance. For more information, see [Use load balancing to distribute Amazon ECS service traffic](service-load-balancing.md). + If your VPC is updated to change the DHCP options set it uses, you can't apply these changes to existing tasks. Start new tasks with these changes applied to them, verify that they are working correctly, and then stop the existing tasks in order to safely change these network configurations. ## Windows considerations The following are considerations when you use the Windows operating system: + Container instances using the Amazon ECS optimized Windows Server 2016 AMI can't host tasks that use the `awsvpc` network mode. If you have a cluster that contains Amazon ECS optimized Windows Server 2016 AMIs and Windows AMIs that support `awsvpc` network mode, tasks that use `awsvpc` network mode aren't launched on the Windows 2016 Server instances. Rather, they're launched on instances that support `awsvpc` network mode. + Your Amazon EC2 Windows instance requires version `1.57.1` or later of the container agent to use CloudWatch metrics for Windows containers that use the `awsvpc` network mode. + Tasks and services that use the `awsvpc` network mode require the Amazon ECS service-linked role to provide Amazon ECS with the permissions to make calls to other AWS services on your behalf. This role is created for you automatically when you create a cluster, or if you create or update a service, in the AWS Management Console. For more information, see [Using service-linked roles for Amazon ECS](using-service-linked-roles.md). You can also create the service-linked role with the following AWS CLI command. ``` aws iam [create-service-linked-role](https://docs.aws.amazon.com/cli/latest/reference/iam/create-service-linked-role.html) --aws-service-name ecs.amazonaws.com ``` + Your Amazon EC2 Windows instance requires version `1.54.0` or later of the container agent to run tasks that use the `awsvpc` network mode. When you bootstrap the instance, you must configure the options that are required for `awsvpc` network mode. For more information, see [Bootstrapping Amazon ECS Windows container instances to pass data](bootstrap_windows_container_instance.md). + Amazon ECS populates the hostname of the task with an Amazon provided (internal) DNS hostname when both the `enableDnsHostnames` and `enableDnsSupport` options are enabled on your VPC. If these options aren't enabled, the DNS hostname of the task is a random hostname. For more information about the DNS settings for a VPC, see [Using DNS with Your VPC](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-dns.html) in the *Amazon VPC User Guide*. + Each Amazon ECS task that uses the `awsvpc` network mode receives its own elastic network interface (ENI), which is attached to the Amazon EC2 Windows instance that hosts it. There is a default quota for the number of network interfaces that can be attached to an Amazon EC2 Windows instance. The primary network interface counts as one toward this quota. For example, by default a `c5.large` instance might have only up to three ENIs attached to it. The primary network interface for the instance counts as one of those. You can attach an additional two ENIs to the instance. Because each task using the `awsvpc` network mode requires an ENI, you can typically only run two such tasks on this instance type. For more information about the default ENI limits for each instance type, see [IP addresses per network interface per instance type](https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/using-eni.html#AvailableIpPerENI) in the *Amazon EC2 User Guide*. + When hosting tasks that use the `awsvpc` network mode on Amazon EC2 Windows instances, your task ENIs aren't given public IP addresses. To access the internet, launch tasks in a private subnet that's configured to use a NAT gateway. For more information, see [NAT gateways](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html) in the *Amazon VPC User Guide*. Inbound network access must be from within the VPC that is using the private IP address or routed through a load balancer from within the VPC. Tasks that are launched within public subnets don't have access to the internet. + Amazon ECS recognizes only the ENIs that it has attached to your Amazon EC2 Windows instance. If you manually attached ENIs to your instances, Amazon ECS might attempt to add a task to an instance that doesn't have enough network adapters. This can result in the task timing out and moving to a deprovisioning status and then a stopped status. We recommend that you don't attach ENIs to your instances manually. + Amazon EC2 Windows instances must be registered with the `ecs.capability.task-eni` capability to be considered for placement of tasks with the `awsvpc` network mode. + You can't manually modify or detach ENIs that are created and attached to your Amazon EC2 Windows instances. This is to prevent you from accidentally deleting an ENI that's associated with a running task. To release the ENIs for a task, stop the task. + You can only specify up to 16 subnets and 5 security groups in `awsVpcConfiguration` when you run a task or create a service that uses the `awsvpc` network mode. For more information, see [AwsVpcConfiguration](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_AwsVpcConfiguration.html) in the *Amazon Elastic Container Service API Reference*. + When a task is started with the `awsvpc` network mode, the Amazon ECS container agent creates an additional `pause` container for each task before starting the containers in the task definition. It then configures the network namespace of the `pause` container by running the [amazon-ecs-cni-plugins ](https://github.com/aws/amazon-ecs-cni-plugins) CNI plugins. The agent then starts the rest of the containers in the task so that they share the network stack of the `pause` container. This means that all containers in a task are addressable by the IP addresses of the ENI, and they can communicate with each other over the `localhost` interface. + Services with tasks that use the `awsvpc` network mode only support Application Load Balancer and Network Load Balancer. When you create any target groups for these services, you must choose `ip` as the target type, not `instance`. This is because tasks that use the `awsvpc` network mode are associated with an ENI, not with an Amazon EC2 Windows instance. For more information, see [Use load balancing to distribute Amazon ECS service traffic](service-load-balancing.md). + If your VPC is updated to change the DHCP options set it uses, you can't apply these changes to existing tasks. Start new tasks with these changes applied to them, verify that they are working correctly, and then stop the existing tasks in order to safely change these network configurations. + The following are not supported when you use `awsvpc` network mode in an EC2 Windows configuration: + Dual-stack configuration + IPv6 + ENI trunking ## Using a VPC in dual-stack mode When using a VPC in dual-stack mode, your tasks can communicate over IPv4, or IPv6, or both. IPv4 and IPv6 addresses are independent of each other. Therefore you must configure routing and security in your VPC separately for IPv4 and IPv6. For more information about how to configure your VPC for dual-stack mode, see [Migrating to IPv6](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-migrate-ipv6.html) in the *Amazon VPC User Guide*. If you configured your VPC with an internet gateway or an outbound-only internet gateway, you can use your VPC in dual-stack mode. By doing this, tasks that are assigned an IPv6 address can access the internet through an internet gateway or an egress-only internet gateway. NAT gateways are optional. For more information, see [Internet gateways](https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Internet_Gateway.html) and [Egress-only internet gateways](https://docs.aws.amazon.com/vpc/latest/userguide/egress-only-internet-gateway.html) in the *Amazon VPC User Guide*. Amazon ECS tasks are assigned an IPv6 address if the following conditions are met: + The Amazon EC2 Linux instance that hosts the task is using version `1.45.0` or later of the container agent. For information about how to check the agent version your instance is using, and updating it if needed, see [Updating the Amazon ECS container agent](ecs-agent-update.md). + The `dualStackIPv6` account setting is enabled. For more information, see [Access Amazon ECS features with account settings](ecs-account-settings.md). + Your task is using the `awsvpc` network mode. + Your VPC and subnet are configured for IPv6. The configuration includes the network interfaces that are created in the specified subnet. For more information about how to configure your VPC for dual-stack mode, see [Migrating to IPv6](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-migrate-ipv6.html) and [Modify the IPv6 addressing attribute for your subnet](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-ip-addressing.html#subnet-ipv6) in the *Amazon VPC User Guide*.