# I am unable to attach network interface to ec2 instances

**URL:** <https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058>\
**Category:** Terraform\
**Created:** [July 28, 2020, 9:45am UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058 "2020-07-28T09:45:54Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![sharathmankala](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/sharathmankala/32/1475_2.png) [@sharathmankala](https://discuss.hashicorp.com/u/sharathmankala)\
**Post date:** [July 28, 2020, 9:45am UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/1 "2020-07-28T09:45:54Z")

</div>

Hi ALL,  
I am planning to create network interface and attach to ec2 instace primary IP, but i am getting below error,Please help me.

on main.tf line 25, in resource “aws\_instance” “ec2\_instance”:  
25: network\_interface = [for nic\_idx in range(aws\_network\_interface.test):

An argument named “network\_interface” is not expected here. Did you mean to  
define a block of type “network\_interface”?

```auto

provider "aws" {
  shared_credentials_file = "/c/Users/test/.aws/credentials"
  profile = "sandbox"
  region = "us-east-1"

}
resource "aws_network_interface" "test" {
  subnet_id = "subnet-*"
  security_groups = ["sg*"]
  count = "${var.number_of_instances}"
}

// EC2 Instance Resource for Module
    resource "aws_instance" "ec2_instance" {
    ami = "${var.ami_id}"
    count = "${var.number_of_instances}"
    instance_type = "${var.instance_type}"
    subnet_id = "${var.subnet_id}"
    vpc_security_group_ids = ["${aws_security_group.apigee-instance.id}"]
    key_name = "java"

    network_interface = [for nic_idx in range(aws_network_interface.test):
      {
      device_index = nic_idx
      network_interface_id = aws_network_interface.test[nic_idx].id
      delete_on_termination = false
    }
  ]
    ebs_block_device {
    device_name = "/dev/sdg"
    volume_type = "gp2"
    volume_size = 200
    delete_on_termination = true
  }
  ebs_block_device {
    device_name = "/dev/sdf"
    volume_type = "gp2"
    volume_size = 20
    delete_on_termination = true
  }
  ebs_block_device {
    device_name = "/dev/sdh"
    volume_type = "gp2"
    volume_size = 10
    delete_on_termination = true
  }

}

```

---

<div class="post-metadata">

**Author:** ![alisdair](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/alisdair/32/4227_2.png) [@alisdair](https://discuss.hashicorp.com/u/alisdair)\
**Post date:** [July 28, 2020, 1:44pm UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/2 "2020-07-28T13:44:36Z")

</div>

The issue here is that your configuration is assigning an argument (using `network_interface = […]`, but it should be using a block (no `x = y` assignment, just `x {…}`).

To use `for_each` with blocks, please [refer to the `dynamic` blocks documentation](https://www.terraform.io/docs/configuration/expressions.html#dynamic-blocks). In this case, I think the below configuration should do what you’re trying to do:

```auto
resource "aws_instance" "ec2_instance" {
  ami = var.ami_id
  instance_type = var.instance_type
  count = var.number_of_instances

  dynamic "network_interface" {
    for_each = aws_network_interface.test
    content {
      device_index = network_interface.key
      network_interface_id = network_interface.value.id
      delete_on_termination = false
    }
  }
}

```

Please note that I have never actually tried creating and assigning AWS network interfaces in this way, so it may not be a best practice—I’m just trying to help with the Terraform language semantics where I can. Hopefully someone with more practical experience can chime in if there’s a better way to do this!

---

<div class="post-metadata">

**Author:** ![sharathmankala](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/sharathmankala/32/1475_2.png) [@sharathmankala](https://discuss.hashicorp.com/u/sharathmankala)\
**Post date:** [July 28, 2020, 4:09pm UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/3 "2020-07-28T16:09:36Z")

</div>

Hi @alisdair,  
Sill i ma getting error like below

```auto
Error: Incorrect attribute value type

  on main.tf line 28, in resource "aws_instance" "ec2_instance":
  28: network_interface_id =aws_network_interface.test[*].id
    |----------------
    | aws_network_interface.test is tuple with 2 elements

Inappropriate value for attribute "network_interface_id": string required.

Error: Incorrect attribute value type

  on main.tf line 28, in resource "aws_instance" "ec2_instance":
  28: network_interface_id =aws_network_interface.test[*].id
    |----------------
    | aws_network_interface.test is tuple with 2 elements

Inappropriate value for attribute "network_interface_id": string required.

Error: Incorrect attribute value type

  on main.tf line 28, in resource "aws_instance" "ec2_instance":
  28: network_interface_id =aws_network_interface.test[*].id
    |----------------
    | aws_network_interface.test is tuple with 2 elements

Inappropriate value for attribute "network_interface_id": string required.

Error: Incorrect attribute value type

  on main.tf line 28, in resource "aws_instance" "ec2_instance":
  28: network_interface_id =aws_network_interface.test[*].id
    |----------------
    | aws_network_interface.test is tuple with 2 elements

Inappropriate value for attribute "network_interface_id": string required.

```

```auto
// Provider specific configs

provider "aws" {
  shared_credentials_file = "/c/Users/ag64160/.aws/credentials"
  profile = "sandbox"
  region = "us-east-1"

}
resource "aws_network_interface" "test" {
  subnet_id = "subnet-06de28df4461194be"
  security_groups = ["sg-0de4b3a45f739ee0f"]
  count = "${var.number_of_instances}"
}

// EC2 Instance Resource for Module
    resource "aws_instance" "ec2_instance" {
    ami = "${var.ami_id}"
    count = "${var.number_of_instances}"
    instance_type = "${var.instance_type}"
    subnet_id = "${var.subnet_id}"
    vpc_security_group_ids = ["${aws_security_group.apigee-instance.id}"]
    key_name = "psdev"
    dynamic "network_interface" {
    for_each = aws_network_interface.test
    content {
      device_index = 1
      network_interface_id =aws_network_interface.test[*].id
      delete_on_termination = false
    }
}
    ebs_block_device {
    device_name = "/dev/sdg"
    volume_type = "gp2"
    volume_size = 200
    delete_on_termination = true
  }
  ebs_block_device {
    device_name = "/dev/sdf"
    volume_type = "gp2"
    volume_size = 20
    delete_on_termination = true
  }
  ebs_block_device {
    device_name = "/dev/sdh"
    volume_type = "gp2"
    volume_size = 10
    delete_on_termination = true
  }

}

```

---

<div class="post-metadata">

**Author:** ![alisdair](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/alisdair/32/4227_2.png) [@alisdair](https://discuss.hashicorp.com/u/alisdair)\
**Post date:** [July 28, 2020, 4:25pm UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/4 "2020-07-28T16:25:22Z")

</div>

Did you try the configuration as I suggested? Quoted again:

> [@alisdair](#):
>
> ```auto
> dynamic "network_interface" {
> for_each = aws_network_interface.test
> content {
> device_index = network_interface.key
> network_interface_id = network_interface.value.id
> delete_on_termination = false
> }
> }
> 
> ```

Did this not work?

---

<div class="post-metadata">

**Author:** ![sharathmankala](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/sharathmankala/32/1475_2.png) [@sharathmankala](https://discuss.hashicorp.com/u/sharathmankala)\
**Post date:** [July 28, 2020, 5:30pm UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/5 "2020-07-28T17:30:35Z")

</div>

HI @alisdair,  
Yes its working, but when am creating instances it creating 2 network interfaces,  
i need only one network interface.  
how to get that,Please help me.

FYR i am updating plan state

```auto
Terraform will perform the following actions:

  # aws_instance.ec2_instance[0] will be created
  + resource "aws_instance" "ec2_instance" {
      + ami = "ami-0e8f1415d9ba49d82"
      + arn = (known after apply)
      + associate_public_ip_address = (known after apply)
      + availability_zone = (known after apply)
      + cpu_core_count = (known after apply)
      + cpu_threads_per_core = (known after apply)
      + get_password_data = false
      + host_id = (known after apply)
      + id = (known after apply)
      + instance_state = (known after apply)
      + instance_type = "t2.micro"
      + ipv6_address_count = (known after apply)
      + ipv6_addresses = (known after apply)
      + key_name = "psdev"
      + network_interface_id = (known after apply)
      + outpost_arn = (known after apply)
      + password_data = (known after apply)
      + placement_group = (known after apply)
      + primary_network_interface_id = (known after apply)
      + private_dns = (known after apply)
      + private_ip = (known after apply)
      + public_dns = (known after apply)
      + public_ip = (known after apply)
      + security_groups = (known after apply)
      + subnet_id = (known after apply)
      + tenancy = (known after apply)
      + volume_tags = (known after apply)
      + vpc_security_group_ids = (known after apply)

      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdf"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 20
          + volume_type = "gp2"
        }
      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdg"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 200
          + volume_type = "gp2"
        }
      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdh"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 10
          + volume_type = "gp2"
        }

      + ephemeral_block_device {
          + device_name = (known after apply)
          + no_device = (known after apply)
          + virtual_name = (known after apply)
        }

      + metadata_options {
          + http_endpoint = (known after apply)
          + http_put_response_hop_limit = (known after apply)
          + http_tokens = (known after apply)
        }

      + network_interface {
          + delete_on_termination = false
          + device_index = 0
          + network_interface_id = (known after apply)
        }
      + network_interface {
          + delete_on_termination = false
          + device_index = 1
          + network_interface_id = (known after apply)
        }

      + root_block_device {
          + delete_on_termination = (known after apply)
          + device_name = (known after apply)
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = (known after apply)
          + volume_type = (known after apply)
        }
    }

  # aws_instance.ec2_instance[1] will be created
  + resource "aws_instance" "ec2_instance" {
      + ami = "ami-0e8f1415d9ba49d82"
      + arn = (known after apply)
      + associate_public_ip_address = (known after apply)
      + availability_zone = (known after apply)
      + cpu_core_count = (known after apply)
      + cpu_threads_per_core = (known after apply)
      + get_password_data = false
      + host_id = (known after apply)
      + id = (known after apply)
      + instance_state = (known after apply)
      + instance_type = "t2.micro"
      + ipv6_address_count = (known after apply)
      + ipv6_addresses = (known after apply)
      + key_name = "psdev"
      + network_interface_id = (known after apply)
      + outpost_arn = (known after apply)
      + password_data = (known after apply)
      + placement_group = (known after apply)
      + primary_network_interface_id = (known after apply)
      + private_dns = (known after apply)
      + private_ip = (known after apply)
      + public_dns = (known after apply)
      + public_ip = (known after apply)
      + security_groups = (known after apply)
      + subnet_id = (known after apply)
      + tenancy = (known after apply)
      + volume_tags = (known after apply)
      + vpc_security_group_ids = (known after apply)

      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdf"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 20
          + volume_type = "gp2"
        }
      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdg"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 200
          + volume_type = "gp2"
        }
      + ebs_block_device {
          + delete_on_termination = true
          + device_name = "/dev/sdh"
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + snapshot_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = 10
          + volume_type = "gp2"
        }

      + ephemeral_block_device {
          + device_name = (known after apply)
          + no_device = (known after apply)
          + virtual_name = (known after apply)
        }

      + metadata_options {
          + http_endpoint = (known after apply)
          + http_put_response_hop_limit = (known after apply)
          + http_tokens = (known after apply)
        }

      + network_interface {
          + delete_on_termination = false
          + device_index = 0
          + network_interface_id = (known after apply)
        }
      + network_interface {
          + delete_on_termination = false
          + device_index = 1
          + network_interface_id = (known after apply)
        }

      + root_block_device {
          + delete_on_termination = (known after apply)
          + device_name = (known after apply)
          + encrypted = (known after apply)
          + iops = (known after apply)
          + kms_key_id = (known after apply)
          + volume_id = (known after apply)
          + volume_size = (known after apply)
          + volume_type = (known after apply)
        }
    }

  # aws_network_interface.test[0] will be created
  + resource "aws_network_interface" "test" {
      + id = (known after apply)
      + mac_address = (known after apply)
      + outpost_arn = (known after apply)
      + private_dns_name = (known after apply)
      + private_ip = (known after apply)
      + private_ips = (known after apply)
      + private_ips_count = (known after apply)
      + security_groups = [
          + "sg-0de4b3a45f739ee0f",
        ]
      + source_dest_check = true
      + subnet_id = "subnet-06de28df4461194be"

      + attachment {
          + attachment_id = (known after apply)
          + device_index = (known after apply)
          + instance = (known after apply)
        }
    }

  # aws_network_interface.test[1] will be created
  + resource "aws_network_interface" "test" {
      + id = (known after apply)
      + mac_address = (known after apply)
      + outpost_arn = (known after apply)
      + private_dns_name = (known after apply)
      + private_ip = (known after apply)
      + private_ips = (known after apply)
      + private_ips_count = (known after apply)
      + security_groups = [
          + "sg-0de4b3a45f739ee0f",
        ]
      + source_dest_check = true
      + subnet_id = "subnet-06de28df4461194be"

      + attachment {
          + attachment_id = (known after apply)
          + device_index = (known after apply)
          + instance = (known after apply)
        }
```

---

<div class="post-metadata">

**Author:** ![alisdair](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/alisdair/32/4227_2.png) [@alisdair](https://discuss.hashicorp.com/u/alisdair)\
**Post date:** [July 28, 2020, 5:45pm UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/6 "2020-07-28T17:45:57Z")

</div>

Oh, I see! I completely misunderstood what you’re trying to do. I thought you wanted all network interfaces to be bound to each AWS instance.

I now think you’re trying to create, say, 5 `aws_network_interface` resources and 5 `aws_instance` resources, and assign them one-to-one. That does make more sense 😅

In that case, I think you want to bind the network interface using an address with `count.index`, like this:

```auto
resource "aws_instance" "ec2_instance" {
  ami = var.ami_id
  instance_type = var.instance_type
  count = var.number_of_instances

  network_interface {
    device_index = 0
    network_interface_id = aws_network_interface.test[count.index].id
    delete_on_termination = false
  }
}

```

I hope that’s clearer. Again, I haven’t used this configuration with AWS, so if anyone would care to offer corrections or recommend best practices, that would be great!

---

<div class="post-metadata">

**Author:** ![sharathmankala](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/sharathmankala/32/1475_2.png) [@sharathmankala](https://discuss.hashicorp.com/u/sharathmankala)\
**Post date:** [August 1, 2020, 5:45am UTC](https://discuss.hashicorp.com/t/i-am-unable-to-attach-network-interface-to-ec2-instances/12058/7 "2020-08-01T05:45:02Z")

</div>

Hi @alisdair,  
Its working, Thanks.  
I have one more question  
How to assign tag to specific node (eg count= 5) in terraform.  
usecase:  
creating 5 nodes using count =5, but i need a specific tag to 2nd and 5th node,  
is it possible via terraform.