Customer Gateway IP address

Most enterprise Oracle customers will create an IPSec VPN tunnel from their data center to AWS.  A customer gateway is required at the customer location/data center and a virtual private gateway on the AWS side.   The customer gateway IP address will be the public external IP address of the on-premise device (supported devices can be found here:http://aws.amazon.com/vpc/faqs/#C8). For example, if the public IP of the customer device is 203.200.25.8 and you plan to use this device to connect to AWS via VPC, then you will need to use this IP as the customer gateway.

Extending your home or small business network to AWS VPC

Extending you home, small business, data center, co lo, or enterprise offices to AWS running VPC, you will probably want to run an IPSEC tunnel.  AWS lists the certified VPN devices here:  http://aws.amazon.com/vpc/faqs/#C9.  However, if you are doing this from a home or small office connection, you may not want to use an expensive dedicated device.  In this case the open source pfSense makes sense: www.pfsense.org. It can used to create an inexpensive IPSEC tunnel to AWS VPC using any hardware you have 'laying around'. 

Getting started with AWS VPC

Most enterprise customer using Oracle on AWS will be using AWS VPC.  A great place to start is:
aws.amazon.com/vpc.  This web site also has a nice explanation and a step by step for setting up VPC with an IPsec tunnel. http://complaintsincorporated.com/2012/07/27/amazon-vpc-adventure-customer-gateway-on-the-cheap/