Cisco Packet Tracer is a network simulation program that allows students to try the features of different Cisco platforms and to test network behaviours.
It supports multiple platforms of routers, switches and even ASA firewall. PCs, servers, laptops, and WAN components are supported as well.
The latest version is Packet Tracer 6.1 (released in June 2014) and the most important change since the last release is the addition of Cisco ASA platform. There are other new features/enhancements added as well.
Cisco Packet Tracer has an intuitive GUI that allows students to build complex topologies by simply drag-and-dropping the devices. Once you connect those devices, you are good to go to configure the network as you like.
Intense School offers a quite impressive variety of Packet Tracer labs which covers different Cisco certification tracks. Most of these labs are for CCNA Routing and Switching. However, limited topics from CCNA Security and CCNA Voice are also covered. A few labs do not exactly fall into any of these categories, but they cover topics that are quite popular.
Therefore, the Packet Tracer labs are split into CCNA R&S topics, CCNA Security topics, CCNA Voice topics and miscellaneous topics.
CCNA Routing and Switching Topics
The books follow a logical progress where more complex notions are preceded by strong foundations from previous chapters.
The first step after you access your devices would be to configure users, passwords, and the authentication method that will be performed on the devices.
CCNA ICND1 Labs
Part I / Chapter 8: Configuring Ethernet Switching from ICND1 introduces the features that are common for both switches and routers. Both of them support secure access, such as by using AAA. You can practice AAA with both local authentication and Radius/Tacacs+ authentication by using this simulation: CCNA Prep: Configuring AAA.
Part I / Chapter 9: Implementing Ethernet Virtual LANs introduces specific topics related to switching, such as VLAN Trunking Protocol (VTP), which you can practice here: CCNA Prep: Creation and Use of a VTP Domain; and inter-VLAN routing, which you can practice here: CCNA Prep: Inter-VLAN Routing. Also, the same chapter provides guidance on how to configure other features on Cisco switches. These features can be further explored by reviewing this article: CCNA Prep: Configuring LAN Switches.
Part VI / Chapter 22: Basic IPv4 Access Control Lists discusses the basics of ACLs. You can use the simulation covered in this article: CCNA Prep: A scenario with Access Lists to get a feeling of standard ACLs using Packet Tracer.
The last topic from ICND1 that is covered by a Packet Tracer simulation is found on Part VI / Chapter 24: Network Address Translation. NAT can be practiced with Packet Tracer by going through this article: CCNA Prep: NAT/PAT Protocol.
CCNA ICND2 Labs
Part II: IP Version 4 Routing / Chapter 7: Virtual Private Networks discusses VPN technologies. Generic Routing Encapsulation (GRE) is a topic for the CCNA exam. You can use this article: CCNA prep: Configuring Generic Routing Encapsulation, which contains a Packet Tracer simulation to practice GRE.
Because there is no networking without routing protocols, ICND2 touches this topic in a very comprehensive way. In ICND2, OSPF is covered in chapters Part III: IP Version 4 Routing Protocols and Chapter 8: Implementing OSPF for IPv4. EIGRP is covered in Part III: IP Version 4 Routing Protocols and Chapter 10: Implementing EIGRP for IPv4.
There are quite a few Packet Tracer labs that you could use to improve your OSPF and EIGRP knowledge. These are: CCNA Prep: Configuring EIGRP, CCNA Prep: Configuring OSPF, CCNA Prep: Troubleshooting OSPF and CCNA Prep: Configuring OSPF Areas.
The corresponding Packet Tracer labs for the WAN part of the ICND2 book are available as well. Part VI / Chapter 12: Implementing Point-to-Point WANs and Part VI / Chapter 14: Implementing Frame Relay cover this. As for Packet Tracer simulations, you can use these resources: CCNA prep: Configuring Point-to-Point WANs and CCNA Prep: A Scenario with Frame Relay.
IPv6 is also covered by a Packet Tracer simulation and you can find it here: CCNA Prep: A Routing Scenario with IPv6: Dual Stack.
There is one more article, CCNA Prep: Configuring IP Services, which covers several topics from both ICND1 and ICND2. The topics are DHCP from ICND1 Part IV / Chapter 18: Configuring and Verifying Host Connectivity, HSRP from ICND2 Part II / Chapter 6: Creating Redundant First-Hop Routers and SYSLOG/NTP/SNMP from ICND2 Part VI / Chapter 19: Managing Network Devices.
CCNA Security Topics
CCNA Security topics are covered well by Packet Tracer simulations. If you want to harden the security on your switches at Layer 2, you can use this article: CCNA prep: Configuring Layer 2 Security.
If GRE tunnels are not enough for you, then maybe you can take a look at IPSec tunnels here: CCNA Prep: Configuring IPSec VPN.
If standard/extended ACLs are not enough for you and you would like to transition to a more stateful firewall feature, then take a look at CBAC here: CCNA Prep: Configuring Context-Based Access Control.
The IPS section from CCNA Security is covered here: CCNA prep: Configuring Intrusion Prevention System.
And last, but not least, the Zone Based Policy Firewall is covered here: CCNA prep: Configuring Zone-Based Policy Firewall.
CCNA Voice Topics
There are two Packet Tracer labs for CCNA Voice as well. Packet Tracer is not very well developed yet for CCNA Voice topics. But you can experiment with basic features to familiarize yourself with IP Phones and Call Manager Express. You can access them here: CCNA Voice Prep: VoIP -Basic Labs and CCNA Voice Prep: VoIP – Intermediate Labs.
Miscellaneous Topics There is a lab covering Wireless LANs. But again, there is not that much that you can do in Packet Tracer with regards to WLANs. This article covers pretty much everything about it: Packet Tracer lab: Wireless LANs (WLAN).
Another article from the miscellaneous section is for PPPoE. The lab can be downloaded here: CCNA Prep: Configuring Point-to-Point Protocol over Ethernet.
Other topics that are supported by Packet Tracer in a limited way are QoS and BGP. However, the features that are supported for these two topics are enough to give you a feeling of what they are and how a basic configuration looks like. You can access the labs here: Packet Tracer lab practice: Configuring BGP and CCNA Prep: Configuring Quality of Service.
As you can see, the Packet Tracer labs cover a lot of topics on the CCNA R&S exam blueprint.
Also, other tracks are covered at a smaller scale, but they should be enough to give you a good start until you get your hands on the particular devices needed for these certifications.
I hope the summary and ordering in this article will make your life easier when you decide to go through the Packet Tracer labs.