Hi kartik,
Welcome to the App Engine Google group. Unless I'm mistaken, I believe your question may be better suited to the
Compute Engine group. As such, I would strongly advise that you post there for some likely more helpful or targeted advice. We also monitor that forum.
In the meantime, I would also suggest familiarizing yourself with
Configuring an Instance's IP Addresses. This should have the information you need to configure a given instance's internal and external IPs outside of what is required from RHEL. Hope this helps!
When posting on the Compute Engine discussion forum, please share a link to your post here so others finding this post can follow through.
Nicholas