EasyClient is a feature of the Internet Gate that eases connection to IPSec servers.
When using a standard IPSec connection the subnets of all connecting clients must be different from each other.
When EasyClient is enabled outgoing packets are NAT-ed to the client gateway's global IP address before entering the IPSec tunnel. This way the client's subnet address is obscured and becomes unimportant. Thus the clients no longer need to all be on separate subnets.
You enable EasyClient on the IPSec Settings page, after clicking “Add” or “Edit/view” in the IPSec - Overview page (or advanced users on the VPN Connection Settings page).
A drawback using EasyClient is that while you can contact computers on the remote network, they cannot contact you. While this limitation is of no significance in most scenarios where you are a client connecting to a network, it still means you must disable EasyClient in connections there you are the server side, or in connections between equal parts. Also some applications not compatible with NAT might get problems working.
Therefore you are recommended to:
If the other end of the IPSec connection is other brand than Internet Gate then configure it as if it would connect to a single PC running IPSec software, thus:
Consult that IPSec gateway's manual for how to configure it for use against single PC clients.