T-Systems Nova This document highlights some of the issues that should be considered when IPSec [2] and Mobile IP [3] inter-work with each other. This work finds some applications in the following fields: VPN traversal requirement [4], IPSec Remote access client co-located with a Mobile Node, IPSec security Gateway running in parallel with a Home Agent or a MIP Proxy [5]. The purpose of this document is informational. Rather that strictly indicating how both protocol should take advantages of each other (IPSec running on top of Mobile IP or the other way around), which is a subjective task left to the user and implementation developers of both protocol, it rather proposes some usage guidelines and general considerations regarding the preference of one solution over the other one.