Archive for certified

Invisible Networks (No Kidding), the World of Virtual LANs (VLANS), Part III

Posted in Cisco Certification with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on June 7, 2011 by jjrinehart

Oops...I Forgot to Turn Off VTP

The history of technology and innovation is full of attempts to create greater efficiencies and automate tasks, a good example is DHCP; this protocol hands out IP address information with little intervention needed.  Any engineer/technician that has had to renumber a network can certainly appreciate this particular task being simplified.  On the other hand, if someone brings in a home router and plugs it in, it can wreak havoc for every other user.

The focus of this post centers on a switching technology that also had good intentions but can create outages that turn an engineer’s hair gray or loose, namely, Virtual Trunking Protocol, or VTP.  The intention of VTP was to simplify the configuration of VLANs across multiple switches.  In a network of less than a dozen devices, manually configuring VLANs is not that big of a deal, but in a large campus environment of a hundred or more switches this becomes ridiculously difficult.  Why not just configure this once and let it propagate automatically?  Seems like a win-win right?  Hold that thought while we go through some specifics.

There are three operational modes of VTP on a Cisco switch (yes, this is a Cisco proprietary protocol), as follows:

  1. Server: This switch serves in a master operational mode, where all the changes are made and then passed out to switches.  To ensure that the latest data is propagated accurately, each time the database changes, the revision number is incremented.
  2. Client: This switch does not store any VLAN information locally, nor can any changes be made to the information it contains.  Think of it as a “read only” mode of operation.
  3. Transparent: A switch in transparent mode operates independently, just as it would if VTP didn’t even exist.  It ignores all updates, though it does pass those updates to all other switches it has trunk links too.  Since VTP cannot be shut off, this is about the closest you can get to off.  If all switches are in a network are configured in this mode it effectively negates any effect it could have on the environment.

Now that you have an idea of how VTP operates, you can appreciate the “gotchas” that come with using it.  If only one switch operates as the server and the rest are all clients, then life is good.  But what happens when you add a new switch in server mode?  Hopefully nothing, unless the configuration revision number just so happens to be higher than the one that all the other switches have.  At that point, “poof” (see picture above), the database on every single switch is immediately erased.  The technical term for this is RGE–Resume Generating Event.  Best practices recommend just operating in transparent mode.

Talk to you later…

– Joe


CCNA Lab Projects

Posted in Cisco Certification with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on June 2, 2011 by jjrinehart

I normally do not post more than once a day but wanted to get these documents back out there, I have created another CCNA Lab Project that was an absolute blast to come up with.  It’s amazing what you can create with just a pen and paper while taking off in an airplane!

Here are the highlights:

  1. Simulated Metro-Ethernet Primary Network
  2. Internet Access at Remote Sites
  3. VPN/GRE Backup Network
  4. Multiple Routing Protocols
  5. A Few Mind Bending Twists Thrown In

Here are the links to the documents, I deployed this in my own lab and will be compiling an answer key for #2.  Enjoy!

Project 1:

CCNA Lab Project Document 12-18-2010

Project 2:

** Just Added Project #3 **

– Joe

CCNA Networking Fundamentals: Part 1

Posted in Cisco Certification with tags , , , , , , , , , , , , , , , , , , , , , on March 31, 2011 by jjrinehart

To have a complete knowledge needed to successfully achieve the CCNA certification, you and I need to have a good grasp of how networks move information from one place to another.  Since all the bits, bytes, masks, and rules can be confusing, I am a big fan of analogies, comparing the concepts to something more familiar.

Networking is really just communication,  namely, communication between electronic devices, which is similar to the process of a conversation.  In classic communication theory, you have the following elements in most situations:

1. Sender.  One individual is creating the information and initiating the conversation.  This person has a series of thoughts or ideas that he/she wants to convey to another person.

2. Receiver.  One individual is receiving the information being sent by the sender.  Ideally, the thoughts or ideas of the sender will be accurately reproduced in the mind of the receiving person.

3. Medium.  No, this doesn’t mean a psychic (nice try though), bur rather, the way in which the message is being sent and received.  In conversations, this is typically the air by means of sound.

All three of these elements actively participate in the actual communication process, which happens in the following manner.  Keep in mind that in a real conversation this process is repeated constantly, and the roles of sender and receiver switch back and forth:

1.  Thoughts: This/these are the concepts in the mind of the sender wanting to be conveyed.

2.  Words: Since humans are not usually psychic, the idea(s) have to be converted into a format suitable for transmission.  This is referred to as encoding.

3.  Transmission: Words are spoken audibly, creating sound waves which travel from the mouth of the speaker to the ear of the listener.  Hopefully he/she is paying attention!

4.  Reception: The receiver/listener hears the sound waves, and the words are interpreted in their mind.  This is the reverse process of #2, and predictably referred to as decoding.

5.  Thoughts:  Using the meaning(s) of the words, the receiver reconstructs the concept/idea in their mind, hopefully reflecting the original.

Sounds simple, right (no pun intended)?  Any of us that have been in any sort of significant relationship, however, can attest that many times the idea understood on the other end of the conversation isn’t even close to the same (“how does this dress make me look?”)  There are lots of things that can distort the message, including language (even accents), background noise, nature of the relationship, and cultural understandings.  The same is true with network communication, which we will look at in more detail in the next post.

My Cisco Certification Journey

Posted in Cisco Certification with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on March 15, 2011 by jjrinehart

I started in the world of Cisco networking in 1998 after a ten year career as an ordained minister.  My first job was at a regional Internet Service Provider as a sales rep, and to be honest, I knew almost nothing about the inner workings of the technology.  To get up to speed, I went to the library and checked out Novell’s Internet Plumbing Handbook.  Unfortunately, most of it was way over my head, was a little discouraging at first, so I read it again…and again…until it started sinking in.  Initially, I had no intention of going the engineering route; I just didn’t want to be a “talking head” or “sales drone” that didn’t have a clue as to how the technology worked.  The funny thing is that once you have the “secret decoder ring,” it’s pretty cool knowing how all the pieces of networking technology fit together.  With my appetite for knowledge growing, I decided to start studying for the Cisco Certified Network Associate (CCNA) certification (this was in early 2000), and passed the exam shortly after.  For me, that was the beginning of my certification journey, culminating in achieving the CCIE in December of 2004.  All of my work in that regard began as self-funded (it took me five times to pass), and I learned a ton along the way.  Since becoming the president of the Seattle Cisco Users Group (, I have discovered a passion for teaching, allowing me to assist others in making the same journey as I have.  I look forward to passing some of the experience through my blog, which will hopefully be useful to those that read it.