Questions about private IP usage.
Do private IPs count against bandwidth usage, and are they restricted to the data center they reside in?
Private network traffic does not count against your monthly transfer quota. Only outbound traffic on your Linode's public IP addresses count against your quota.
Also, Linode private IP addresses are limited to the data center they reside in. They can communicate with other Linodes in the same data center, but cannot reach anything outside without using the public IP.
For more information about adding and using a private IP, check out our guide.