Virtual software-defined networking (SDN) is becoming one of the most interesting and appealing topics in our industry. This talk will cover the challenges of scalability that cloud-scale, distributed virtual SDN solutions face. Duarte will go over the gory details of hardening distributed ARP tables and of replicating the NAT state of distributed routers, all the while ensuring packets are processed at ludicrous speed. The talk will cover the problem space, what tradeoffs are involved, and how these issues are solved in Midonet, an open source network virtualization system.