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- Stopping and restarting the instance after adding a second network interface will release any automatically assigned public IP address. If several interfaces are required where one or more are configured with a public address, use Elastic IP addresses.
- Additionally, adding a second IP network interface to a non-Amazon Linux EC2 instance causes traffic flow issues. This occurs in cases of asymmetric routing where traffic to the instance arrives at one network interface and leaves the instance through the other network interface. This is blocked by AWS because a mismatch between MAC address and IP address. Refer to the AWS documentation and AWS Networking and Charon-SSP (asymmetric routing considerations) for more information. Failure to use the proper steps, may make your instance unreachable!
- If your instance supports enhanced networking there may be naming inconsistencies when adding additional interfaces to a running instance. Please refer to the interface names section in AWS Networking and Charon-SSP.
- The NetworkManager is disabled on Charon-SSP AWS. Therefore, ifcfg-files in /etc/sysconfig/network-scripts are required to define the IP configuration of an interface.
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The initial automatically assigned public IP address will be removed as soon as you restart the instance after adding a network interface with an Elastic IP address to your instance. Do not restart your instance before you are sure you can reach it via the Elastic IP address. The automatically assigned public IP address will also be disabled if you assign an Elastic IP address to the primary Ethernet interface of the instance.
The table below describes the steps required to add an Elastic IP address to a network interface.
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