I have recently been investigating router simulators and have found several on the internet with free demos. After reviewing them I have narrowed down the available packages to four manufactures. The following is my opinion of each of these.
Dynamips is available for free and runs on Linux, Mac OS X or Windows and can simulate the hardware of the Cisco series routing platforms by directly booting actual Cisco IOS software image into the emulator. It allows users to build complex network topologies to test the functionality of IOS on a desktop PC, without the need of an actual physical Cisco device. Dynamips currently supports different networking medium such as Ethernet, Serial link, ATM, and POS interfaces for the Cisco 1700, 2600, 3600, 3700, 7200 and Juniper router hardware platforms as well as Cisco PIX and ASA security platforms.
Even though there are switching platforms included in the application, there is no configuration on them but simple port vlans. There is no VTP, STP or ether-channel configuration and of course no layer 3 switching.
Once installed you must install an appropriate Cisco IOS for every routers and security platforms you wish to use. The switches require no IOS as they have no configuration capabilities. A frame-relay switch is included and be configured with a number of virtual circuits and DLCIs. Dynamips does not support ISDN.
This product is easy to install and use as long as you have access to the Cisco IOS for the devices, and even though it has no labs or tutorials included the price is right. I would recommend this product for anyone studying for the CCNA or routing portion of the CCNP. The inclusion of the PIX, ASA, and IDS security devices give it the added capability for security labs. I would not recommend it for those studying for the CCIE due to the lack of switch configuration.
The Boson simulator NETSIM is available in three variations. The CCENT (99.00), CCNA (179.00), and CCNP (349.00). Each comes with additional functionality as the price increases.
Netsim will simulate 47 different Cisco devices. Cisco 800, 1000, 1600, 1700, 2500, 2600, 2811, 3600 routers; 1900, 2900, 3500 switches and 7960 IP Phone. It also supports a several networking medium such as Ethernet, Serial, ISDN and Frame-Relay. As well as Simulates network traffic with virtual packet technology and SDM emulation.
Netsim provides more switch configuration than any other simulator on the market today, but still cannot match that of hardware as switches use ASIC design to do the switching and software has not been capable of completely emulating yet.
Netsim includes an extensive collection of CCNA and CCNP labs, tutorials and can support up to 233 IOS commands depending on which version of the software you purchase. Although it has no provision for security labs it does have limited VOIP capability.
Netsim is easy to install and requires no additional software or IOS to use. Although it is pricey I would recommend it to anyone studying for the CCNA or CCNP.
SemSim, Cert Exams and Others:
SemSim, Cert Exams and a number of other simulator available are inexpensive usually about 30 to 40 dollars and most do have labs and tutorials included as well as practices exams in some cases. This said it is my opinion that they lack functionality and ease of use. Myself I would opt for the Dynamips product over these products. It may not have the labs but the price is right.
Any product you get will provide additional hands on training but should not be you only training media. You should always purchase good books such as Cisco press and practices exams to supplement you training materials. Remember when you take the test you will not be asked to configure a lab at least not till you are ready for the CCIE.