OppBSD integrates essential parts of the real FreeBSD networking stack into OMNeT++ as a simulation model. Every simulated host (or router) runs its own copy of the FreeBSD kernel’s networking stack. Consequently, the simulation model is very accurate, i.e., almost behaving like a real implementation. Release 4.0 works with OMNeT++ v4.3 (alternatively v4.1, v4.2) and provides IPv6 support. Presently, the package covers the full TCP/IP stack including IPv4, IPv6, UDP, TCP, ICMP, ICMPv6, ARP, ND, sockets and Ethernet frames.