Cisco Packet Tracer - Network Simulator

There are some great tools out there for practicing building computer networks and configuring networking devices.  One such tool is a tool from Cisco known as "Packet Tracer."  Packet Tracer is not a new tool. When I was teaching full time at a Cisco Networking Academy about 20 years ago, we had begun using Packet Tracer in some of our courses.  Back then, it was a very robust tool, but over the years, it has evolved with some incredible features.  Packet Tracer is a free tool that can be downloaded and used to do actual network build simulations or as part of an educational program.  

While it was once commonly assumed that you had to be enrolled in a Cisco Networking Academy course to get and use Packet Tracer, that is no longer the case.  Through the Cisco "Skills for All" program, all you must do is sign up and enroll in one of the many free courses offered by Cisco.  The link above will take you to a course entitled "Getting Started with Cisco Packet Tracer."  It will take you step by step through the download and installation process, then introduce you to how to use Packet Tracer to get started building networks and verifying their operation.  This particular course, as do many of the free Cisco courses, actually includes assessments where you have to use Packet Tracer to successfully configure networks, and answer questions on a final exam that can only be obtained by knowing how to use Packet Tracer to do each task.

Note: Cisco Packet Tracer is a network emulator, as opposed to an actual simulator.  While some of the features are a little limited, the features are robust enough that it is considered as valid and extremely valuable practice for the Cisco CCNA certification.

The video above will give some useful information on downloading and using Packet Tracer, but the Skills for All link above will take you directly to the correct link to sign up.  Also note that the Skills for All link will offer you the latest version of Packet Tracer, which at the time of writing this article is 8.2.0.0162.  Don't worry if some of the information in David's video above is completely over your head!  The information he provides is a good demo of what you can do with Packet Tracer, and there are many free or low-cost courses to get you started.

Credit for the video above goes to the David Bombal YouTube Channel. David Bombal is a Cisco CCIE.  Not only does David have several videos on YouTube, but he has also put together some very good and inexpensive courses on Udemy that will give you the proper foundational skills and practice in preparation for the Cisco CCNA certification.

If you want to get started on using Packet Tracer labs, the Skills for All site has several free courses  that include actual labs that you download, with instructions for completing each step.  There are also free labs that you can download to get started at sites such as "Packet Tracer Labs" and "Packet Tracer Network."  Do an Internet search and you will find others that will work well also.

Download Packet Tracer and get started!

Additional Links:

Cisco Packet Tracer Download (If you do NOT have access to Cisco Networking Academy):

https://youtu.be/fnQB6cN3UWo 

Cisco Packet Tracer 101 Learning Series:  

https://www.youtube.com/playlist?list=PLl9NdZbdtA0wAtO1o9V67lPaFcalwgTEJ

Cisco Packet Tracer - Everything You Need to Know:

https://youtu.be/qZB_biPOBwA

Cisco Packet Tracer 2021 - Crash Course:

https://youtu.be/ty0HMs48U1k

Cisco Packet Tracer | Basic Tips and Tricks (2020):

https://youtu.be/cKCB9mIGf7Y

My Cisco Packet Tracer Tutorial Playlist

https://www.youtube.com/playlist?list=PLm9GBPmQ-2Ca0AErAMZuCtPQ9p-Ft9Ks0

Another Cisco Packet Tracer Tutorial Playlist:

https://www.youtube.com/playlist?list=PLB57s6OrG8LjS4rXfvYZd95H5oHPabDcF

Cisco IOS Command Cheat Sheet

Quick post - I wanted to put together a quick post to give a "cheat sheet" for the basic Cisco IOS commands to use as a reference.  The most important command is the help command.  No matter where you are, typing in "?" will always give you information about what commands are available in each mode, and what you can do with those commands.

Here is a quick tutorial on the commands below put together by the danscourses YouTube channel that goes along with this command reference that he put together for the video.  

NOTE: The command reference below is for the most common commands used by a variety of Cisco devices, and are meant to introduce you to the fundamentals.  There are Cisco commands, however, that are sometimes unique to a specific Cisco IOS release, may be added, deprecated, or changed.  Always check the documentation for your specific hardware.

================================= Basic Router Commands ================================= Router> ---User EXEC mode exit Router> ? Router> enable --------------- Router# ---Privileged EXEC mode disable, exit Router# ? ----------------- Router# configure terminal Router(config)# ---Global Config mode exit, end, Ctrl+c, Ctrl+z Router(config)# ? ----------------- Router(config)# line vty 0 15 Router(config)# line console 0 Router(config-line)# ---Line configuration mode exit, end, Ctrl+c, Ctrl+z Router(config-line)# ? ---------------------------- Router(config)# interface gigabitEthernet 0/0/0 Router(config-if)# ---Interface configuration mode exit, end, Ctrl+c, Ctrl+z Router(config-if)# ? ---------------------------- Router# Router# configure terminal Router# show ? Router# show running-config Router# copy running-config startup-config Router# ping 192.168.1.100 Router# traceroute 192.168.1.100 Router# ssh 192.168.1.100 Router# telnet 192.168.1.100 Router# debug ? Router# clock set 07:14:00 October 15 2019 Router# reload --------------------------------- Router(config)# Router(config)# hostname R1 Router(config)# banner motd "No unauthorized access allowed!" Router(config)# enable password class Router(config)# enable secret class12345 //should be a different password than the unencrypted password Router(config)# service password-encryption Router(config)# line vty 0 15 Router(config)# line console 0 Router(config)# interface gigabitEthernet 0/0/0 ---------------------------------------------------- Router(config-line)# Router(config-line)# password cisco Router(config-line)# login Router(config-line)# transport input all (line vty) ---------------------------------------------------- Router(config-if)# Router(config-if)# interface gigabitEthernet 0/0/0 Router(config-if)# int g0/0 //command abbreviation Router(config-if)# ip address 192.168.1.1 255.255.255.0 Router(config-if)# no shutdown ================================= Basic Switch Commands ================================= Switch> ---User EXEC mode exit Switch> enable --------------- Switch# ---Privileged EXEC mode disable, exit ----------------- Switch# configure terminal Switch(config)# ---Global Config mode exit, end, Ctrl+c, Ctrl+z ----------------- Switch(config)# line vty 0 15 Switch(config)# line console 0 Switch(config-line)# ---Line configuration mode exit, end, Ctrl+c, Ctrl+z ---------------------------- Switch(config)# interface vlan 1 Switch(config-if)# ---Interface configuration mode exit, end, Ctrl+c, Ctrl+z ---------------------------- Switch# Switch# configure terminal Switch# show ? Switch# show running-config Switch# copy running-config startup-config Switch# ping 192.168.1.100 Switch# traceroute 192.168.1.100 Switch# ssh 192.168.1.100 Switch# telnet 192.168.1.100 Switch# debug ? Switch# clock set 07:14:00 October 15 2019 Switch# reload --------------------------------- Switch(config)# Switch(config)# hostname R1 Switch(config)# banner motd "No unauthorized access allowed!" Switch(config)# enable password class Switch(config)# enable secret class Switch(config)# service password-encryption Switch(config)# line vty 0 15 Switch(config)# line console 0 Switch(config)# interface vlan 1 ---------------------------------------------------- Switch(config-line)# Switch(config-line)# password cisco Switch(config-line)# login Switch(config-line)# transport input all (line vty) ---------------------------------------------------- Switch(config-if)# Switch(config-if)# interface vlan 1 Switch(config-if)# ip address 192.168.1.2 255.255.255.0 Switch(config-if)# no shutdown Switch(config-if)# exit Switch(config)# ip default-gateway 192.168.1.1

========================= Extra Helpful Commands: ========================= Router# show ip interface brief //Gives you information about the IP configuration of each interface. Great for troubleshooting.

Router(conf)# no ip domain-lookup //prevents miss-typed commands from being "translated..." Router(conf-line)# logging synchronous //prevents logging output from interrupting your command input

Additional Information:

My Cisco IOS Playlist (Check often as I update it frequently): https://www.youtube.com/playlist?list=PLm9GBPmQ-2CaovCCrLM9gkvNgmhLej53j

Cisco IOS Command Configuration Fundamentals Command Reference: https://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book.html

10 Commands You Should Master When Working with the Cisco IOS:
https://www.techrepublic.com/article/10-commands-you-should-master-when-working-with-the-cisco-ios-104071/

Computer Network Systems - IPv4 Subnetting

My first post in a while - apologies for the long absence.  Since retiring, MJ and I woke up one day and decided that we needed to move back to South Dakota to be with family, so we took most of 2021 to do everything we needed to do to move.  2022 has been a year of getting settled, but since returning, some friends of mine twisted my arm to return to teaching IT stuff.  

Since going back to teaching computer networking topics, I have rediscovered how important it is to grasp the distinct number systems that are used by computers and computer networks.  I have also rediscovered that grasping conversions by these different number systems can be a little difficult.  We humans can easily understand our decimal number system of "1, 2, 3, 4, 5, 6, etc." But computers and networks, however, only understand a "binary" system made up of "1's" and "0's."  And adding to the confusion, we often must express numerical values in another system called the "hexadecimal" system, made up of "0 - 9" and "A - F."

Understanding how these number systems are used is foundational to understanding both IPv4 and IPv6 IP addresses, computer MAC addresses, and even checksum hash values such as MD-5.  It is necessary to not only understand how they are used, but how to convert between the different number systems so that we can understand the concept of "subnetting" which is a key component of how computers on a network communicate.  Without subnetting, using a limited pool of IPv4 addresses was very inefficient back in the day.  But using subnetting, we can split up a local area network into "segments" and make IP addressing more efficient.

I often spend at least a few class periods explaining number systems and subnetting, so I wanted to post a quick list of rather good tutorials that go along with the Cisco CCNA curriculum, as I have found these to be quite easy to understand.

Credit goes to DansCourses YouTube Channel for putting together these excellent tutorials.