OpenNHRP implements NBMA Next Hop Resolution Protocol (as defined in RFC 2332). It makes it possible to create dynamic multipoint VPN Linux router using NHRP, GRE and IPsec. It aims to be Cisco DMVPN compatible.
Great piece of software, working like a charm.
Very easy to use opennhrp
It was a little trick to get it working with ipsec-tools alpha version , but in the end it worked just fine. Here is the software we used to create a encripted tunnel with a working "multicast-enabled-VPN" : Kernel: linux-2.6.32-5 , (CONFIG_ARPD=y), (modules loaded: xfrm4_tunnel, authenc, xfrm4_mode_tunnel;) Multicast Sofware: quagga-0.99.16, qpimd-0.161. VPN Software: ipsec-tools 0.8-alpha20090903, opennhrp-0.11.2