Drag and drop your network design, give it your address block. The configurator graphically assigns subnet masks and IP addresses to every host and gateway.
stuff to read
Complete Cisco VPN Specifications (MS Word format).
A paper to document a secure site-to-site VPN tunnel between 2 Cisco firewalls with
overlapping internal address spaces (in the example, both use 192.168.x.x).
Includes configuration files for both sides with every line carefully explained.
This paper is appropriate for professional use.