“A positive mind finds a way it can be done; a negative mind looks for all the ways it can’t be done.” Napoleon Hill
Hands-On Practice – GNS3 Video Training Course
I remember the “Music Man” story, where a trickster wanted an entire community to believe that the students could learn to play their musical instruments (which they didn’t physically have) by simply visualizing it. That doesn’t work for someone who has never touched an instrument, and it also doesn’t work for a learner who is studying Cisco networking but has never practiced using the commands.
One of the challenges for the Cisco student is accessing live gear so that he or she can practice implementation, verification and troubleshooting of both simple and complex network configurations. For individuals with limited access to network equipment, many have turned to simulators, which are programs that mimic the look and feel of the network hardware. Another option is to use a hardware emulator (called a hypervisor), that creates a virtual environment on a host computer. By running Cisco IOS software on a hypervisor, complex networking scenarios can be created and the real look and feel of hardware devices can be experienced, although ultimately it is the the Cisco IOS operating system that the learner interacts with.
GNS3 and Hypervisors
Many years ago, an open source hypervisor (named Dynamips) was written to emulate Cisco routers. Dynamips was intended to emulate Cisco IOS hardware, and was fairly complicated to implement, which put it out of reach of the average learner. More recently, a Graphical User Interface (GUI) was added to manage the process of the hypervisor, and the GUI is currently called the Graphic Network Simulator (GNS3). Today, using your own computer as the host machine running Windows, Linux or Mac OSX, you can build and create a virtual network, all living within the software on your computer.
GNS3 is the front-end for multiple hypervisors, including Dynamips and Qemu (the Quick Emulator). Qemu can be used to emulate hardware used by the Cisco Adaptive Security Appliance (ASA) firewall. What this means to the learner is that in GNS3, he or she can quickly set up routers and firewalls, using simple drag and drop actions on the screen. Adding Ethernet connections between the devices is done by a couple of mouse clicks. Additional hardware modules (such as serial or Ethernet port modules) can be added to the routers in the virtual GNS3 topology for more complex network designs.
GNS3 supports hardware emulation for several models of Cisco routers, but doesn’t provide the actual IOS. Many learners choose to purchase a single physical router, and use the related IOS image in their virtual GNS3 topology as they test, practice, learn and confirm their networking skills. Layer 2 Ethernet switching inside of a GNS3 topology is limited to the switchport modules that can be added to the virtual routers inside of GNS3, which doesn’t support the full layer 2 switching capabilities that a physical switch would provide. As a result, many people want to have interaction between their GNS3 network and live network gear, which they can do by using logical Ethernet connections. And, if desired, they can set up 802.1q or ISL trunks between the devices in GNS3 and live physical network devices.
Several interesting possibilities for GNS3 exist, including:
• Using Windows, Linux or MAC OSX as the host computer for GNS3
• Integrating the host computer as a node on the GNS3 network(s)
• Virtual PC integration (VMware, VirtualBox) into GNS3 topologies
• Virtual PC Simulator to create several virtual “PCs” on a GNS3 network
• Ethernet and Trunking capabilities between GNS3 devices and live networks
• Virtual “appliances” as nodes on the GNS3 network
• Distributed computing GNS3 hypervisor support
• Router, ASA, and Switchport module emulation
• Wireshark Integration for GNS3 protocol analysis of GNS3 network traffic
• Cisco Configuration Professional (CCP) access to GNS3 routers
• ASDM (ASA Security Device Manager) GUI access to GNS3 firewalls
GNS3 (and its associated hypervisors) can be downloaded at http://www.GNS3.net
Challenges with GNS3
When I am with other learners who are working to improve their skills associated with Cisco routers and firewalls, I will often ask how many are actively using GNS3. There are always a few who use it and love it. Others haven’t yet heard of it, but most people indicate they have tried it, yet simply aren’t using it. Why is this? Common answers include “I didn’t have time to figure it out”, or “I tried it and my CPU pegged at 100% so I simply gave up.”
There are some very real pitfalls to be avoided with GNS3, which is easy if you know what they are. Some of the very basic mistakes include:
• Not understanding/tuning the “idle-PC” value
• Not opening a console session after starting the virtual router, or
• Allowing a console session to reach the inactivity timer
Each of these issues is simple to fix, but users must be aware of them.
In several cases, when talking with students, a basic explanation is all it takes to change the situation from GNS3 being something they tried and left alone, to GNS3 being one of the most significant tools they use both for practicing, and for proof-of-concept designs, protocol analysis and verification.
GNS3 Video Training Course
There is a lot of information on the Internet regarding GNS3 and how to get it working successfully. Unfortunately, not all of the information is either current or accurate, and finding the “gems” of knowledge that work for you may take a lot of time – if you do indeed find the correct information.
In November, Dan Charbonneau of CBT Nuggets asked Keith Barker if he would gather up his experiences with GNS3 and build an effective, no-nonsense training series so that people who wanted to use GNS3 could make it work for them. Keith jumped at the chance, as he knew it will make a huge difference in the “hands-on” experience for many learners and network professionals.
The GNS3 video training course is available now through CBT Nuggets, for those interested in acquiring hands-on practice of Cisco network equipment. The series is available for USD $5 through December 26, at the following URL: http://www.cbtnuggets.com/it-training-videos/series/gns3
