IP Restructuring

Hi,

Years ago someone set up our internal IP addressing scheme with the unique numbering of 192.168.1….
This obviously causes a problem when someone is trying to VPN from a location that is also using the same ID. So we are going to renumber everything. We are running a point to point T1 with Active Directory 2000 my main concern. Can anyone point me in the direction of some articles or checklists on this subject? Or thoughts of their own? Thanks! CT