There are multiple implementations around such as Openswan, Libreswan, and strongSwan.
NetModule Routers used Openswan as the IPSec Framework until Version 3.8.
Starting with 4.0 we switched to StrongSwan with IKEv2 Support
Cisco SSL AnyConnect VPN allows remote users to access enterprise networks from anywhere on the Internet through an SSL VPN gateway using a web browser. During the establishment of the SSL VPN with the gateway, the client downloads and installs the AnyConnect VPN client from VPN gateway.
Cisco ASA 5500-X products support SSL AnyConnect VPN.
The Linux client implementation is openconnect. There is also a server implementation called ocserv.
NetModule Routers currently do not ship with Cisco SSL VPN support. If you want to do some tests, ask for a test image.
Using standards-based IPsec technology, Cisco IOS Easy VPN greatly simplifies VPN deployment with centralized VPN management across all Cisco VPN devices. It supports integration of a variety of remote devices within a single deployment and with a consistent policy and key management method, which simplifies remote side administration.
Supported Cisco products include Cisco ASA 5500 Series, Cisco VPN 3000 Series, and Cisco PIX Firewall.
The Linux client implementation is vpnc. There is no known server implementation. The client does not support Network-Extension Mode (NEM).
NetModule Routers currently do not ship with Cisco EasyVPN support. If you want to do some tests, ask for a test image.