Using Instance Addressing

Amazon Elastic Compute Cloud: 2009-04-04

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Using Instance Addressing

Topics

API Overview
  • Determining Your IP Addresses
  • Using Elastic IP Addresses

    • This section describes how to perform common instance addressing tasks.

    API Overview

    This section provides a brief overview of each elastic IP address operation.

    • AllocateAddress—Acquires an elastic IP address for use with your account.

    • DescribeAddresses—Lists elastic IP addresses assigned to your account.

    • ReleaseAddress—Releases an elastic IP address associated with your account.

      After releasing an elastic IP address, it is released to the IP address pool and might no longer be available to your account.

    • AssociateAddress—Associates an elastic IP address with an instance.

    • DisassociateAddress—Disassociates the specified elastic IP address from the instance to which it is assigned.

    Determining Your IP Addresses

    This section describes how to determine your internal and external IP addresses.

    AWS Management Console

    To determine your private and public IP addresses

    1. Log in to the AWS Management Console and click the Amazon EC2 tab.

    2. Click Instances in the Navigation pane.

      The console displays a list of running instances.

    3. Locate and select an instance.

      The console displays information about the instance in the lower pane.

    4. To determine the public IP address, use the IP address specified within the Public DNS field.

    5. To determine the private IP address, use the IP address specified within the Private DNS field.

    Command Line Tools

    To determine your private IP address in Linux and UNIX

    1. Connect to the instance.

    2. Enter one of the following commands:

      • # ifconfig eth0

      • # curl http://169.254.169.254/latest/meta-data/local-ipv4

        The second option refers to the instance data. For more information, see Instance Metadata.

    To determine your private IP address in Windows

    1. Connect to the instance.

    2. On the taskbar, click Start, right-click My Computer, and select Properties.

    3. Click the Computer Name tab. The IP address appears in the Full computer name field.

    To determine your public IP address

    1. Connect to the instance.

    2. Determine your public IP address from your instance by referring to the instance data.

      PROMPT> curl http://169.254.169.254/latest/meta-data/public-ipv4

    Using Elastic IP Addresses

    Elastic IP addresses are static IP addresses designed for dynamic cloud computing. An elastic IP address is associated with your account, not a particular instance. You control addresses associated with your account until you choose to explicitly release them.

    This section describes how to perform common elastic IP address tasks.

    Allocating Elastic IP Addresses

    This section describes how to assign an Amazon EC2 elastic IP address to your account and verify it.

    AWS Management Console

    To allocate a new IP address for use with your account

    1. Log in to the AWS Management Console and click the Amazon EC2 tab.

    2. Click Elastic IPs in the Navigation pane.

      The console displays a list of elastic IP addresses assigned to your account.

    3. Click Allocate New Address.

      A confirmation dialog box appears.

    4. Click Yes, Allocate.

      A new elastic IP address appears in the list.

    Command Line Tools

    To allocate a new IP address for use with your account

    • Enter the following command:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-allocate-address

      Amazon EC2 returns an elastic IP address similar to the following:

      ADDRESS 75.101.155.119
    [Note] Note

    An Elastic IP address is associated with an account and billed accordingly until the address is released using ec2-release-address command.

    Describing Elastic IP Addresses

    This section describes how to view the elastic IP addresses allocated to your account.

    AWS Management Console

    To view elastic IP addresses assigned to your account

    1. Log in to the AWS Management Console and click the Amazon EC2 tab.

    2. Click Elastic IPs in the Navigation pane.

      The console displays a list of elastic IP addresses assigned to your account.

    3. To reduce the size of the list, start typing part of the IP address or instance ID to which it is assigned in the search box.

    Command Line Tools

    To view elastic IP addresses assigned to your account

    1. To view all elastic IP addresses assigned to your account::

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-addresses

      Amazon EC2 returns a list of elastic IP addresses similar to the following:

      ADDRESS 75.101.157.145
	ADDRESS 75.101.155.119

    2. To verify a specific elastic IP address:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-addresses ip_address

      Amazon EC2 returns the specified elastic IP address, similar to the following:

      ADDRESS 75.101.157.145

    Associating an Elastic IP Address with a Running Instance

    Once an elastic IP address is allocated, you can map it to a running instance.

    AWS Management Console

    To associate an elastic IP address with an instance

    1. Log in to the AWS Management Console and click the Amazon EC2 tab.

    2. Click Instances in the Navigation pane.

      The console displays a list of running instances.

    3. Write down the instance ID to associate with the elastic IP address.

    4. Click Elastic IPs in the Navigation pane.

      The console displays a list of elastic IP addresses assigned to your account.

    5. Select an instance and click Associate.

      The Associate Address dialog box appears.

    6. Select the instance from the Instance ID list box and click Associate.

      The elastic IP address is associated with the instance.

    Command Line Tools

    To associate an elastic IP address with an instance

    1. Describe running instances:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-instances

      Amazon EC2 returns output similar to the following:

      RESERVATION      r-ae33c2c7      924417782495    default
INSTANCE         i-b2e019da      ami-2bb65342    ec2-72-44-33-67.compute-1.amazonaws.com  ip-10-251-71-165.ec2.internal   running  gsg-keypair     0               m1.small        2008-03-03T23:09:09+0000       us-east-1a
INSTANCE         i-b2e019db      ami-2bb65342    ec2-67-202-3-83.compute-1.amazonaws.com  ip-10-251-47-36.ec2.internal    running  gsg-keypair     1               m1.small        2008-03-03T23:09:09+0000       us-east-1a

      Write down the instance ID to associate with an elastic IP address.

    2. Describe elastic IP addresses assigned to the account:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-addresses

      Amazon EC2 returns a list of elastic IP addresses similar to the following:

      ADDRESS 75.101.157.145
ADDRESS 75.101.155.119

      Write down the elastic IP address to associate with an instance.

    3. To associate the instance and elastic IP address:

      PROMPT> ec2-associate-address -i instance_id ip_address

      Amazon EC2 returns output similar to the following:

      ADDRESS 75.101.157.145   i-b2e019da

    4. Associations take a few minutes to complete. To verify the association using ec2-describe-addresses:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-addresses

      Amazon EC2 returns output similar to the following:

      ADDRESS 75.101.157.145   i-b2e019da

    5. To verify the association using ec2-describe-instances:

      PROMPT> ec2-describe-instances-i instance_id

      Amazon EC2 returns output similar to the following:

      RESERVATION      r-ae33c2c7      924417782495    default
INSTANCE         i-b2e019da      ami-2bb65342    ec2-75-101-157-145.compute-1.amazonaws.com  ip-10-251-71-165.ec2.internal   running  gsg-keypair     0               m1.small        2008-03-03T23:09:09+0000       us-east-1a

    Associating an Elastic IP Address with a Different Running Instance

    Once an Elastic IP Address is allocated, you can map it to a different running instance.

    [Note] Note

    It is highly unlikely that an instance will be configured with its original public IP address that it used prior to being mapped.

    AWS Management Console

    To remap an IP address

    1. Log in to the AWS Management Console and click the Amazon EC2 tab.

    2. Click Instances in the Navigation pane.

      The console displays a list of running instances.

    3. Write down the new instance ID to associate with the elastic IP address.

    4. Click Elastic IPs in the Navigation pane.

      The console displays a list of elastic IP addresses assigned to your account.

    5. Locate the IP address to remap and click Disassociate.

      A confirmation dialog box appears.

    6. Click Yes, Disassociate.

      The elastic IP address is disassociated from the instance and you are returned to the list of elastic IP addresses assigned to your account.

    7. Locate the IP address in the list and click Associate.

      The Associate Address dialog box appears.

    8. Select the new instance from the Instance ID list box and click Associate.

      The elastic IP address is associated with the new instance.

    Command Line Tools

    To remap an IP address

    1. Describe running instances:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-instances

      Amazon EC2 returns output similar to the following:

      RESERVATION      r-ae33c2c7      924417782495    default
INSTANCE         i-b2e019da      ami-2bb65342    ec2-67-202-46-87.compute-1.amazonaws.com    ip-10-251-71-165.ec2.internal   running  gsg-keypair     0               m1.small        2008-03-03T23:09:09+0000       us-east-1a
INSTANCE         i-b2e019db      ami-2bb65342    ec2-75-101-157-145.compute-1.amazonaws.com  ip-10-251-47-36.ec2.internal    running  gsg-keypair     1               m1.small        2008-03-03T23:09:09+0000       us-east-1a

      Write down the instance ID to associate with an elastic IP address.

    2. Associate the address with a new instance:

      PROMPT> ec2-associate-address -i instance_id ip_address

      Amazon EC2 returns output similar to the following:

      ADDRESS 75.101.157.145   i-b2e019da

    3. Verify the changes:

                      PROMPT> 
                
                  
                    
                  
                
                ec2-describe-instances

      Amazon EC2 returns output similar to the following:

      RESERVATION      r-ae33c2c7      924417782495    default
INSTANCE         i-b2e019da      ami-2bb65342    ec2-75-101-157-145.compute-1.amazonaws.com    ip-10-251-71-165.ec2.internal   running  gsg-keypair     0               m1.small        2008-03-03T23:09:09+0000       us-east-1a
INSTANCE         i-b2e019db      ami-2bb65342    ec2-67-202-46-39.compute-1.amazonaws.com  ip-10-251-47-36.ec2.internal    running  gsg-keypair     1               m1.small        2008-03-03T23:09:09+0000       us-east-1a

    Example

    In the following example, web servers are connected to the Internet through elastic IP addresses and to database servers through their private IP addresses.

    The administrator decides to replace a web server with a larger instance type. To do this, the administrator starts a new instance using a larger instance type (1), disassociates an elastic IP address from a running instance (2), associates the elastic IP address with the new instance (3), and terminates the old instance (4).

    AWS Management Console Example

    The following demonstrates how to set up these tasks using the AWS Management Console.

    Launch Process

    1

    The user clicks Instances in the Navigation pane.

    The console displays a list of running instances.

    2

    The user clicks Launch Instance, specifies settings that meet the new requirements, and clicks Launch.

    3

    The user clicks Elastic IPs in the Navigation pane.

    The console displays a list of elastic IP addresses assigned to the account.

    4

    The user selects the desired IP address that is assigned to another instance, clicks Disassociate, and confirms the disassociation.

    The user is returned to the list of elastic IP addresses.

    5

    The user locates the IP address in the list, clicks Associate, selects the new instance, and confirms the association.

    The elastic IP address is assigned to the new instance.

    6

    The user clicks Instances in the Navigation, selects the old instance, and clicks Terminate.

    Amazon EC2 begins shutting down the old instance.

    Command Line Tools Example

    The following demonstrates how to set up these tasks using the command line tools. 

    PROMPT> ec2-run-instances ami-6ba54002 -n 1 --availability-zone us-east-1a 
RESERVATION r-a034c7c9 924417782495 default
INSTANCE i-3ea74257 ami-6ba54002 pending 0 m1.large 2007-07-11T16:40:44+0000 us-east-1a

PROMPT> ec2-disassociate-address 67.202.55.255 
ADDRESS 67.202.55.255

PROMPT> ec2-associate-address -i i-3ea74257 67.202.55.255 
ADDRESS 67.202.55.255   i-43a4412a

PROMPT> ec2-terminate-instances i-4bc32334
INSTANCE i-4bc32334 running shutting-down
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