Prakash Iyer Multi-subnetted IEEE 802.11 WLAN networks are being widely deployed in Enterprise Intranets –(in many cases requiring a VPN tunnel to connect back and access Intranet resources), and public areas such as airports, coffee shops, convention centers and shopping malls. Many of these WLAN networks also employ NAT to translate between non-routable and routable IPv4 care-of (point of attachment) addresses. WWAN networks such as those based on GPRS, 1xRTT and eventually EDGE, 1xEV, CDMA2000 and UMTS are also starting to see deployment. These deployments are paving the way for applications and usage scenarios requiring TCP/IP session persistence and constant reachability while connecting back to a secured (VPN protected), target “home” network. This in turn drives the need for a mobile VPN solution that is multi-vendor interoperable, providing seamless access with persistent VPN sessions - through NAT gateways when needed. This draft proposes a solution framework that enables efficient, seamless operation of Mobile IPv4 when combined with an IPsec-based VPN and supporting NAT traversal when needed. The solution has no link layer dependencies and can be applied to other 802.3-compatible wired and wireless physical media as well.