How to combine AWS and dedicated external servers?

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http://serverfault.com – I have an extensive network of servers all currently hosted on AWS EC2. For reasons of cost I plan to gradually migrate to dedicated servers where possible. So: How can I best combine AWS and non-AWS servers in my network? Ideally, I should be able to assign internal IP addresses to the external servers, include them in AWS security groups and ensure that all private traffic between my AWS servers and external servers is secure. (HowTos)