Looking for VPN suggestion

Hello,

VPN solutions I have used previously dynamically assign an office LAN
IP to the connecting client for the duration of the VPN session. All
traffic to/from the connected client route through the VPN gateway at
the office.

Is there an open source VPN solution that will allow Windows and Linux
clients to connect to our office machines in a similar manner?

I've looked at Freeswan and OpenVPN, and it seems that they don't
behave in the way I described.

Thanks