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. With the introduction of Cisco Packet Tracer 5.3 and 6.0, several new features were added, including BGP, HSRP, which are part of the CCNP TM curriculum. Despite some feature limitations, students preparing CCNP Route and CCNP Switch exams are also able to simulate basic IP telephony with Cisco Call Manager Express and IPSEC VPN using Cisco 2811 routers.
After months of waiting, Cisco Packet Tracer 6.1 has finally been released by Cisco in late August 2014. The new Cisco Packet Tracer version has been released with the version number 6.1.1 and is available in two versions : "Cisco Packet Tracer Student" and "Cisco Packet Tracer Instructor". Cisco Packet Tracer 6.1 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 ...
While Cisco Packet Tracer aims to provide a realistic simulation of functional networks, the application itself utilizes only a small number of features found within the actual hardware running a current Cisco IOS TM and focuses on CCENT / CCNA preparation. Work on real Cisco hardware (switches & routers) or GNS3 simulation software is hardly recommended for a good preparation for CCNP exam simulation questions.
Update 13/02/2015 : Packet Tracer 6.2 is available for download. This new version provides 3G/4G telephony support as well as a new Cisco 819 ISR router. OSPF and EIGRP enhancements also included. Packet Tracer 6.2 feature list available on our Cisco Packet Tracer 6.2 page.