Problem

When deploying BOSH instances with multiple network interfaces (using different nic_group configurations) and an Elastic IP, the CPI fails during create_vm with:

CPI error 'Unknown' with message 'There are multiple interfaces attached to instance 'i-xxxxx'. 
Please specify an interface ID for the operation instead.'

Additionally, there was no way to control which NIC receives the Elastic IP in multi-NIC configurations.

Root Cause

The associate_address AWS API call was using the instance_id parameter, which according to AWS documentation only works when "the instance must have exactly one attached network interface."

AWS Documentation Reference

From the AWS EC2 AssociateAddress API Documentation:

InstanceId parameter:

"The ID of the instance. The instance must have exactly one attached network interface. You can specify either the instance ID or the network interface ID, but not both."

NetworkInterfaceId parameter:

"The ID of the network interface. If the instance has more than one network interface, you must specify a network interface ID. You can specify either the instance ID or the network interface ID, but not both."

Solution

Multi-NIC Elastic IP fix:

• Use network_interface_id instead of instance_id in associate_address call
• Query instance network interfaces and target the correct NIC based on nic_group

nic_group support for VIP networks:

• Users can specify which NIC receives the Elastic IP via nic_group in deployment manifest
• Director passes nic_group to CPI, which maps it to the corresponding device_index
• Backward compatible: defaults to primary NIC (device_index 0) when not specified

Additional improvements:

• Added retry logic for AWS API calls to handle transient failures
• Enhanced error messages with device_index and nic_group details

Depends on cloudfoundry/bosh#2658