Cisco Packet Tracer is a powerful network simulator that can be utilized in training for CCNA TM and CCNP TM certification exam by allowing students to create networks with an almost unlimited number of devices and to experience troubleshooting without having to buy real CiscoTM routers or switches.
Cisco Packet Tracer features an array of simulated Application layer protocols (HTTP, DNS, …), as well as basic routing with RIP, OSPF, and EIGRP, to the extent required by the current CCNA TM curriculum. It also includes Cisco IOS 15 with licence features which was introduced in the CCNA exam in 2013.
Cisco Packet Tracer 6.3 has been released on 22th december 2015 by Cisco. This is a maintenance version with netacad login enabled at application startup. It replaces Cisco Packet Tracer 6.2 Student and Cisco Packet Tracer 6.2 Instructor. Cisco Packet Tracer 6.2 includes an ASA 5505 firewall with command line configuration (but no Adaptive Security Device Manageror CCP tools). It also includes a netflow collector as a Desktop application in the server device, routing protocols for IPv6 (OSPFv3, EIGRPv6 , RIPNg), DHCP snooping commands, IPv6 CEF, IPSEC ...
Packet Tracer 6.2 introduced 3G/4G telephony support as well as a new Cisco 819 ISR router with a embedded wireless Access Point. OSPF and EIGRP enhancements were also added in this new version.
Update 20/06/2016 : Packet Tracer 7.0 build 201 has been released on 17th June 2016. This might be a preview version of the official Packet Tracer 7.x verson expected at the end of the month. This new version includes 3 new Cisco routers (819IOX, 829, 1240 routers), a new IE2000 industral switch, hge protocol improvments, ans new IoE (Internet Of Everything) features.
Update 01/05/2016 : Prepare the CCNA and CCNP datacenter exam using UCS server emulator (UCS PE) and VIRL NXOS simulator. Thse two tools will help you get strong practical experience on the Cisco main datacenter technologies before taking the exam. Enjoy ;-)