OppBSD integrates essential parts of the real FreeBSD networking stack into OMNeT++ as a simulation model. In the model, every simulated host (or router) runs its own copy of the FreeBSD kernel's networking stack, and every host (or router) has its own copy of all state variables of the FreeBSD kernel. Consequently, the simulation model is very accurate, i.e., almost behaving like a real implementation, e.g., it performs duplicate address detection and neighbor discovery just as a normal IPv6 stack would. Presently, the package covers the full TCP/IP stack including IPv4, IPv6, UDP, TCP, ICMP, ICMPv6, ARP, ND, sockets and Ethernet frames. It also allows one to dump internal kernel variables of the tcp control block (e.g., windows sizes, ssthresh, etc.) into an OMNeT++ vector file for later analysis and also provides to dump pcap files for analysis with standard tools like tcpdump or WireShark (formerly known as Ethereal).