Dave's Tech Blog
A Third Eye on Technology

We start with 3 basic layers:

1. Physical – (Cables, radio waves, binary 1′s and 0′s, etc).
2. Data Link – (Switch/Bridge devices/MAC address)
3. Network – (Routers)

Routers are the devices which are given the most focus. Here is the back of an example router:

The look of a router will vary greatly, but it’s function and purpose is essentially the same: Route IP traffic, as well as other management stuff we’ll discuss later.

Within the router is a Command Line Interface called the Cisco IOS. The traditional method used to access this operating system is to attach a rollover cable to the routers console port and the other end to a serial port on a PC. Then, using a terminal emulator like Hyper Terminal (included with Windows for free) to establish a serial connection. These settings need to be correct in order for the connection to work:

• Baud – 9600
• Databits – 8
• Parity – None
• Stop Bits – 1

The Aux port on a router can be setup to accept incoming connections from external devices like a phone modem, allowing for remote administration. Virtual Terminal ports can also be configured, allowing the administrator to set up any of the Ethernet ports on the router to accept incoming remote administrator telnet or SSH sessions.

When you establish a console session with a router, you begin in “user mode”, and you are very limited on what commands the router can accept from you. To escalate your privileges, you type “enable” and press enter. A password prompt can be configured later to ask for a password when this command is entered. A password can also be placed over the user mode as well, to prevent access by unauthorized users.

Tab-Completion of commands is supported, as well as ? inquires. If you type “con?” and press enter, the possible commands that begin with “con” will be displayed. If you type “config ?” sub commands that can be sent to config will be shown. This is handy if you forget your commands.

When a router first powers on, it goes through a Power On Self Test by loading a small ROM chip. This mode seeks out an IOS image file, which is the actual OS. The OS is usually stored on Flash memory.

To configure the router, you have to type “enable” to switch into Privlaged mode, then type “config term”. Then you can begin to configure other interfaces (more on that later).

Once you’re done with changing your configuration, you can save it to your startup config file by typing “copy run start”. You can also erase your config by typing “erase start”.

That’s all for now. More on the way.

CCNA stands for Cisco Certified Networking Associate. It serves as a foundation for other higher level certifications, such as the CCNP and CCIE. The school I recently graduated from provided me with all the knowledge I needed to prepare to take and pass the CCNA exam. Sad thing is, I never attempted to take the test, and essentially decided to opt myself out of it. I just didn’t really feel motivated enough. I was actually de-motivating myself a lot, so was my former employer (I hear they lost two major contracts and they laid off 50 people…had something to do with trying to save money on screws, I think. Darn!)

Let me explain a little more. I used to work for a factory that manufactures garage doors. I worked their for nearly 4 years, starting as a temp and working my way up to staff trainer in under 2 years. Then, one day the training department I was in was downsized. They tried to cover up what they were doing by slotting all trainers who were in soon-to-be-eliminated positions into available department lead positions and told them it was only going to be temporary. I was told that I would be in charge of the warehouse. The WAREHOUSE! Telling 10 other forklift operators what to do and cutting off my personal time even more (preventing me from going to school) didn’t sound like something I was just going to casually let them do to me; I didn’t feel like working 50 or 60 hours a week. So I told them I would rather demote myself than work in a position I didn’t feel interested in fulfilling. They obliged, and my pay was cut by about 3 dollars an hour. I had decided at that point I wasn’t going to work in a garage door factory for the rest of my life, and immediately began investigating their tuition reimbursement program…

I graduated from Kaw Area Technical School about 2 months after leaving that place, continuing to work on the weekends for the data center. And for me, that was enough to survive and pay the bills. I have had ambitions about starting my own tech support business, and as such I kinda slacked off when it came to having a desire to pay the 150 some dollars to take the final CCNA exam. I had already gotten a tech job in a good place with a good boss, and was happy basically taking it easy for a while. I partially felt that if I had kept in step with some other classmates after graduation that I might end up charging my way into being employed for more of the same types of people I despised when working at that garage door factory, which would also conflict with my desire to be completely self employed someday. I would tell myself, “If I’m my own boss, who cares what’s on my resume.” Kinda naive of me, but hey, live and let live. I’m only 25; I’ve got some time on my hands….

Recently, I’ve been churning up my desire to nail that CCNA certification to my wall, as well as go beyond it. CCNP is a must and I’ve also become interested in seeing what there is to get out of a CISSP certification. But that’s way down the road.

I am going to crash through the entire CCNA curriculum tonight, tomorrow evening and through the weekend, and report my progress here. I also intend to write a very skeleton sort of description of many concepts learned. I’ll then take the test, pass and post about my success here for you to read. This shouldn’t be very difficult for me, since most of the networking concepts taught are second nature to me these days.

So stay tuned. You’re going to get schooled in computer networking, and learn a few useful things you could use in the future. I’ll try to make it fun for ya too.