Cisco Router Configuration Tutorial

http://www.joshgentry.com/cisco/cisco.htm

http://www.swcp.com/~jgentry/topo/cisco.htm

Network Calculators

http://www.subnetmask.info/

Classful IP Subnet Calculations

http://www.joshgentry.com/networking/subnet.htm

VPN Setup for Routers - Getting it to work with an IPSec Client

http://www.homenethelp.com/vpn/router-config.asp