Previously, certification exams consisted of only objective type questions such as true/false or multiple choice questions. However, recently more and more certification vendors, including Cisco, are using simulated labs for examining a candidate's expertise in a given situation. For this reason, it is essential that those aspiring for Cisco certifications have sufficient hands-on experience. For this purpose, router simulators are available from a few vendors that simulate an actual router network, but with limited amount of functionality built in. Typically, the commands supported by a router simulator are a sub-set of the full command-set of an actual router. However, simulators are relatively cheap (compared to purchase of physical routers) and cover the command-set required for respective exam objectives.