Use AssociateAddress with an Amazon SDK or CLI

    /// <summary>
    /// Associate an Elastic IP address to an EC2 instance.
    /// </summary>
    /// <param name="allocationId">The allocation Id of an Elastic IP address.</param>
    /// <param name="instanceId">The instance Id of the EC2 instance to
    /// associate the address with.</param>
    /// <returns>The association Id that represents
    /// the association of the Elastic IP address with an instance.</returns>
    public async Task<string> AssociateAddress(string allocationId, string instanceId)
    {
        var request = new AssociateAddressRequest
        {
            AllocationId = allocationId,
            InstanceId = instanceId
        };

        var response = await _amazonEC2.AssociateAddressAsync(request);
        return response.AssociationId;
    }

###############################################################################
# function ec2_associate_address
#
# This function associates an Elastic IP address with an Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Parameters:
#       -a allocation_id - The allocation ID of the Elastic IP address to associate.
#       -i instance_id - The ID of the EC2 instance to associate the Elastic IP address with.
#
# Returns:
#       0 - If successful.
#       1 - If it fails.
#
###############################################################################
function ec2_associate_address() {
  local allocation_id instance_id response

  # Function to display usage information
  function usage() {
    echo "function ec2_associate_address"
    echo "Associates an Elastic IP address with an Amazon Elastic Compute Cloud (Amazon EC2) instance."
    echo "  -a allocation_id - The allocation ID of the Elastic IP address to associate."
    echo "  -i instance_id - The ID of the EC2 instance to associate the Elastic IP address with."
    echo ""
  }

  # Parse the command-line arguments
  while getopts "a:i:h" option; do
    case "${option}" in
      a) allocation_id="${OPTARG}" ;;
      i) instance_id="${OPTARG}" ;;
      h)
        usage
        return 0
        ;;
      \?)
        echo "Invalid parameter"
        usage
        return 1
        ;;
    esac
  done
  export OPTIND=1

  # Validate the input parameters
  if [[ -z "$allocation_id" ]]; then
    errecho "ERROR: You must provide an allocation ID with the -a parameter."
    return 1
  fi

  if [[ -z "$instance_id" ]]; then
    errecho "ERROR: You must provide an instance ID with the -i parameter."
    return 1
  fi

  # Associate the Elastic IP address
  response=$(aws ec2 associate-address \
    --allocation-id "$allocation_id" \
    --instance-id "$instance_id" \
    --query "AssociationId" \
    --output text) || {
    aws_cli_error_log ${?}
    errecho "ERROR: AWS reports associate-address operation failed."
    errecho "$response"
    return 1
  }

  echo "$response"
  return 0
}

The utility functions used in this example.

###############################################################################
# function errecho
#
# This function outputs everything sent to it to STDERR (standard error output).
###############################################################################
function errecho() {
  printf "%s\n" "$*" 1>&2
}

##############################################################################
# function aws_cli_error_log()
#
# This function is used to log the error messages from the AWS CLI.
#
# The function expects the following argument:
#         $1 - The error code returned by the AWS CLI.
#
#  Returns:
#          0: - Success.
#
##############################################################################
function aws_cli_error_log() {
  local err_code=$1
  errecho "Error code : $err_code"
  if [ "$err_code" == 1 ]; then
    errecho "  One or more S3 transfers failed."
  elif [ "$err_code" == 2 ]; then
    errecho "  Command line failed to parse."
  elif [ "$err_code" == 130 ]; then
    errecho "  Process received SIGINT."
  elif [ "$err_code" == 252 ]; then
    errecho "  Command syntax invalid."
  elif [ "$err_code" == 253 ]; then
    errecho "  The system environment or configuration was invalid."
  elif [ "$err_code" == 254 ]; then
    errecho "  The service returned an error."
  elif [ "$err_code" == 255 ]; then
    errecho "  255 is a catch-all error."
  fi

  return 0
}

    Aws::EC2::EC2Client ec2Client(clientConfiguration);

    Aws::EC2::Model::AssociateAddressRequest associate_request;
    associate_request.SetInstanceId(instanceId);
    associate_request.SetAllocationId(allocationId);

    const Aws::EC2::Model::AssociateAddressOutcome associate_outcome =
            ec2Client.AssociateAddress(associate_request);
    if (!associate_outcome.IsSuccess()) {
        std::cerr << "Failed to associate Elastic IP address " << allocationId
                  << " with instance " << instanceId << ":" <<
                  associate_outcome.GetError().GetMessage() << std::endl;
        return false;
    }

    std::cout << "Successfully associated Elastic IP address " << allocationId
              << " with instance " << instanceId << std::endl;

To associate an Elastic IP addresses in EC2-Classic

This example associates an Elastic IP address with an instance in EC2-Classic. If the command succeeds, no output is returned.

Command:

aws ec2 associate-address --instance-id i-07ffe74c7330ebf53 --public-ip 198.51.100.0

To associate an Elastic IP address in EC2-VPC

This example associates an Elastic IP address with an instance in a VPC.

Command:

aws ec2 associate-address --instance-id i-0b263919b6498b123 --allocation-id eipalloc-64d5890a

Output:

{
    "AssociationId": "eipassoc-2bebb745"
}

This example associates an Elastic IP address with a network interface.

Command:

aws ec2 associate-address --allocation-id eipalloc-64d5890a --network-interface-id eni-1a2b3c4d

This example associates an Elastic IP with a private IP address that's associated with a network interface.

Command:

aws ec2 associate-address --allocation-id eipalloc-64d5890a --network-interface-id eni-1a2b3c4d --private-ip-address 10.0.0.85

    public static String associateAddress(Ec2Client ec2, String instanceId, String allocationId) {
        try {
            AssociateAddressRequest associateRequest = AssociateAddressRequest.builder()
                    .instanceId(instanceId)
                    .allocationId(allocationId)
                    .build();

            AssociateAddressResponse associateResponse = ec2.associateAddress(associateRequest);
            return associateResponse.associationId();

        } catch (Ec2Exception e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
        return "";
    }

import { AssociateAddressCommand } from "@aws-sdk/client-ec2";

import { client } from "../libs/client.js";

export const main = async () => {
  // You need to allocate an Elastic IP address before associating it with an instance.
  // You can do that with the AllocateAddressCommand.
  const allocationId = "ALLOCATION_ID";
  // You need to create an EC2 instance before an IP address can be associated with it.
  // You can do that with the RunInstancesCommand.
  const instanceId = "INSTANCE_ID";
  const command = new AssociateAddressCommand({
    AllocationId: allocationId,
    InstanceId: instanceId,
  });

  try {
    const { AssociationId } = await client.send(command);
    console.log(
      `Address with allocation ID ${allocationId} is now associated with instance ${instanceId}.`,
      `The association ID is ${AssociationId}.`,
    );
  } catch (err) {
    console.error(err);
  }
};

suspend fun associateAddressSc(
    instanceIdVal: String?,
    allocationIdVal: String?,
): String? {
    val associateRequest =
        AssociateAddressRequest {
            instanceId = instanceIdVal
            allocationId = allocationIdVal
        }

    Ec2Client { region = "us-west-2" }.use { ec2 ->
        val associateResponse = ec2.associateAddress(associateRequest)
        return associateResponse.associationId
    }
}

Example 1: This example associates the specified Elastic IP address with the specified instance in a VPC.

C:\> Register-EC2Address -InstanceId i-12345678 -AllocationId eipalloc-12345678

Output:

eipassoc-12345678

Example 2: This example associates the specified Elastic IP address with the specified instance in EC2-Classic.

C:\> Register-EC2Address -InstanceId i-12345678 -PublicIp 203.0.113.17

class ElasticIpWrapper:
    """Encapsulates Amazon Elastic Compute Cloud (Amazon EC2) Elastic IP address actions."""

    def __init__(self, ec2_resource, elastic_ip=None):
        """
        :param ec2_resource: A Boto3 Amazon EC2 resource. This high-level resource
                             is used to create additional high-level objects
                             that wrap low-level Amazon EC2 service actions.
        :param elastic_ip: A Boto3 VpcAddress object. This is a high-level object that
                           wraps Elastic IP actions.
        """
        self.ec2_resource = ec2_resource
        self.elastic_ip = elastic_ip

    @classmethod
    def from_resource(cls):
        ec2_resource = boto3.resource("ec2")
        return cls(ec2_resource)


    def associate(self, instance):
        """
        Associates an Elastic IP address with an instance. When this association is
        created, the Elastic IP's public IP address is immediately used as the public
        IP address of the associated instance.

        :param instance: A Boto3 Instance object. This is a high-level object that wraps
                         Amazon EC2 instance actions.
        :return: A response that contains the ID of the association.
        """
        if self.elastic_ip is None:
            logger.info("No Elastic IP to associate.")
            return

        try:
            response = self.elastic_ip.associate(InstanceId=instance.id)
        except ClientError as err:
            logger.error(
                "Couldn't associate Elastic IP %s with instance %s. Here's why: %s: %s",
                self.elastic_ip.allocation_id,
                instance.id,
                err.response["Error"]["Code"],
                err.response["Error"]["Message"],
            )
            raise
        return response

# Associates an Elastic IP address with an Amazon Elastic Compute Cloud
# (Amazon EC2) instance.
#
# Prerequisites:
#
# - The allocation ID corresponding to the Elastic IP address.
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param allocation_id [String] The ID of the allocation corresponding to
#   the Elastic IP address.
# @param instance_id [String] The ID of the instance.
# @return [String] The assocation ID corresponding to the association of the
#   Elastic IP address to the instance.
# @example
#   puts allocate_elastic_ip_address(
#     Aws::EC2::Client.new(region: 'us-west-2'),
#     'eipalloc-04452e528a66279EX',
#     'i-033c48ef067af3dEX')
def associate_elastic_ip_address_with_instance(
  ec2_client,
  allocation_id,
  instance_id
)
  response = ec2_client.associate_address(
    allocation_id: allocation_id,
    instance_id: instance_id,
  )
  return response.association_id
rescue StandardError => e
  puts "Error associating Elastic IP address with instance: #{e.message}"
  return "Error"
end

    TRY.
        oo_result = lo_ec2->associateaddress(                         " oo_result is returned for testing purposes. "
            iv_allocationid = iv_allocation_id
            iv_instanceid = iv_instance_id
        ).
        MESSAGE 'Associated an Elastic IP address with an EC2 instance.' TYPE 'I'.
      CATCH /aws1/cx_rt_service_generic INTO DATA(lo_exception).
        DATA(lv_error) = |"{ lo_exception->av_err_code }" - { lo_exception->av_err_msg }|.
        MESSAGE lv_error TYPE 'E'.
    ENDTRY.