CCNA Obtained

On October 30, 2007, I obtained my CCNA. That was the original point of this blog; to aid me in my pursuit of my CCNA. However, this blog will continue on as I develop myself.

Now that I have my CCNA, I have a taste for Certifications. It is like a Shark; normally, they don't view humans as a source of sustenance. However, once they have tasted an arm or a leg, they will come back for more. At least, that is what I learned by watching Jaws.

Certification is only meaningful if you make it so. I am not making more money today, nor I am truly a better engineer just because I have certificate and wallet card from Cisco. However, my thinking is a little different. I am more confident. I have a sense of accomplishment from setting and achieving a goal. I also have more ammunition when presenting myself as an expert in a situation: Cisco says that I am a CCNA, what have you got?

My company wants us to obtain our Microsoft Desktop Support Technician certificate (MCDST). It is not something I am excited about, but it won't hurt. It consists of the 70-271 and 70-272 exams, and covers your skill at supporting Windows XP on individual PCs in workgroup and domain networks. Passing either exam designates you as a Microsoft Certified Professional (MCP), which is another line on your resume and another logo under your email signature. Successfully passing both exams gets you the MCDST, which will make my VP happy.

Three more tests after that and you are a Microsoft Certified System Administrator (MCSA). That is a little more interesting to me. From MCSA to Microsoft Certified Systems Engineer (MCSE) is just a few more tests. Combining MCSE with a Cisco specialist certification will definitely help out in the marketplace.

Which brings me to what I want to do. I want to get up to speed on firewalls. I have a lot to learn on routers and switches, but I am competent enough now to get the job done. I am not very knowledgeable on VPNs and security using firewalls. In the future, I would like to spend a lot more time on network security. Therefore, in 2008 I will work earnestly towards passing the Cisco 642-552 Securing Network Devices (SND) exam. This will extend my CCNA certification past October 30, 2010. It will also count towards a Cisco Firewall Specialist designation, and ultimately towards the Cisco Certified Security Professional (CCSP), which is like gold.

I have to pay the bills, and my current job is doing that well, so I am buckling down on the 70-271 right now. I hope to pass that during my two weeks of vacation at the end of November. That exam will spell out the rest of my journey. If it is as easy as I hope, then I will complete my MCDST by January and then focus on the Cisco SND exam. If the 70-271 is tricky and requires more brain cells than I am willing to commit, I will scrap it and try to convince the powers that be that my SND is much more valuable to them. Stay tuned.

Helpful Links

Until I get a chance to continue with my OSI Model discussion, I want to post two helpful websites to develop your knowledge of networking:

Firewall: This is a fantastic website full of free information.

Bright Spark/Celtic Rover's Internetworking Gateway: Another fantastic, free site jam-packed with networking information.

OSI: Layer 1 - The Physical Layer

Layer 1 - Physical: This is the wires and connectors of the network, as well as the electrical signal on the wire. Examples that you can see on your computer right now: The network cable that runs to the wall, switch, or cable modem. Also, there is probably a green or amber light next to that cable which is evidence of physical, Layer 1 connectivity. If your network connection is ethernet, the cable plugs into your computer using an RJ45 jack and the cable is called Category 5 (Cat 5; you may have Cat 6 if you are really up to speed). If you are on dial-up, then the phone cable connected to your computer is using an RJ11 jack and Cat 3 (or, twisted-pair) cabling for Layer 1. If your computer is using wireless 802.11 to connect to the internet, then the antennaes and radio signal are the physical, Layer 1 elements.

The physical layer is usually the most common culprit of network connection problems. Cables have a tendency to get unplugged, cut, pinched, damaged, or just plain go bad. Also, it is possible you have the wrong type of cable, there is electrical interference, or power issues. A wise troubleshooter will always verify physical connectivity twice before proceeding with any troubleshooting; I cannot tell you how frustrating it is to troubleshoot for an hour using every advanced resource available to you and then find out that the cable is unplugged.

Layer 1 is the third largest consideration in designing a network, after considering cost-justification and security. You need to make sure you have the right cables and adapters for the network, and that they will be secure from damage, interference, and maliciousness. You also need to plan for the limitations of your signals; cables can only be so long and can only handle so many users. Radio signals are easier to prevent damage to, but are increasingly running into problems with interference and will never be the most secure solution. Radio signals are also faced with many limitations and will make a larger impact in your budget.

The OSI Model Overview

Before I take off more advanced CCNA topics, I feel like I should first re-visit the fundamentals. This will help any reader who is starting out, and it will ensure that I myself am building on a solid foundation. Every baseball player re-visits the fundamentals in spring training camp; by the same hand I know that I would also benefit from some fundamental.

The fundamental concept that builds networks today is the Open Systems Interconnect (OSI) model. This model drives the design of network appliances, network application software, network protocols, and network cabling. It also assists the field engineer with designing and troubleshooting networks. Understanding the OSI Model is essential if you wish to have success at any level or in any function of networking.

The OSI model describes the seven logical layers of networking. This is not something tangible; you cannot hold an OSI layer in your hand or click on an icon to view it. You can hold or click on items that are examples of the OSI concept, but in the end these are just concepts that all the networking geeks have agreed on.

The real purpose of the OSI model when it was first written was to make sure that everyone who designed a piece of hardware or software intended for a network could do so and ensure that it would be compatible with all the other devices in a network. The OSI model is like a framework upon which to build the details of network communications. The details are listed elsewhere, such as by the Internet Engineering Task Force and the Institute of Electrical and Electronic Engineers.

The OSI Model consists of seven layers:

1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application

To remember this order, I like to use the mnemonic phrase Please Do Not Throw Sausage Pizza Away. Another good one, though it is in reverse order: All People Seem To Need Data Processing. A learned a new one (also reversed) tonight: All People Standing Totally Naked Don't Perspire.

In the future, I will describe each layer in a little more depth.

Troubleshooting VLANs

First of all, I should mention that the posts on this blog are not in any particular order. Sometimes, I will just grab a random topic in order to study something. This is how my brain works, and I apologize to the orderly-minded people who consider this chaotic.

Second of all, I am assuming that you are already familiar with this subject. I may skip many fundamentals and jump to the meat. That is exactly what I will do today.

Virtual Local Arean Networks (VLANs) are a means of subdividing switches into broadcast domains. Switches are normally collision domains. If you will have several Layer 3 networks on one switch (such as a network for VOIP and a network for Computers), it is wise and often necessary to create VLANs.

To troubleshoot VLANs on a switch, you can use the following commands:
#show vlan brief (lists the vlans and interfaces in each vlan)
#show vlan id x (replace x with the vlan number you are looking at for status.)
#show spanning-tree vlan x (use this to check root id, discover possible loops)

The New Blog

I have created this second blog because it matches my goals but does not match the theme of my primary blog. Perceptions of Reality is geared more toward social science and topical commentary. This blog focuses on real knowledge in the subject of computer networks. If my opinion appears, it will only do so with a purpose: to make your study and real-world application more effective based on my experiences. Other than that, this blog will real information about networks.

I have been in the IT industry in various roles for ten years. I have never passed the Cisco Certified Network Associate exam though it has been a goal of mine since my first attempt at it in 2000. There are various reasons and excuses for such failures, but I am leaving those behind me. I am now at a point in my life where I can focus on my CCNA, and I will pass it as soon as possible.

My CCNA study is the purpose of this blog. I hope that my writing here helps someone else, but the real purpose here is to focus my study. By encoding knowledge in my head into written form, I learn better--most people do. That is why you write so many papers in school. I will try to write about at least one topic from the CCNA exam every day on this blog until my studies are through.

In the future, I may pursue further certifications in the field. In that case, this blog will live on. Only time will tell. In the meantime, lets learn something together.

If I can be of assistance, or I need to be corrected, please email me: lslobodzian@gmail.com