Just how important are the basics? I mean the real basics? If you were starting all over again in networking, is there something you would make sure you knew before you took the CCNA exam, or the CCNP exams? At what point should you hit the pause button and spend more time getting the basics down before biting off a chunk of advanced technologies? I think these are questions that beginners fail to ask themselves, and worse, fail to understand.
Why is it that the CCNA asks you to learn how to subnet? Most people use a calculator anyhow right? I mean, when am I ever going to have to do that at work? These are some common questions that come up in my CCNA classes. I try to help people understand that much of what you are learning, whether you use it again or not, is going to give you clarity and bring the picture more into focus. For example, say you have an IP address allocation and it's subnetted between multiple sites. There are /30's used over the P2P (Point-to-Point) links and /27's at the branch sites. Do you understand why? Are they contiguous? Can you summarize routes? If you don't see the high-level picture you're going to throw a routing protocol out there, config it just good enough to exchange some routes and pass traffic across sub-optimal paths, and then when it doesn't work as expected you're going to have to call someone in to fix it.
Yes! Take the time to understand subnetting.
Why do I care about the OSI model? I remember the pneumonic All People Seem To Need Data Processing. Isn't that enough? NO! The OSI model, and a specific understanding of the TCP/IP protocol stack gives you an understanding of how packets are built, what devices see when they examine them, how layers work together and so on. There are fundamental concepts like ARP that is a whole lot easier to understand when you know the OSI model and how the layers work together. Ask yourself these questions:
- Why do I need ARP?
- What does it do?
- If ARP didn't exist what would happen on my network?
- What uses ARP?
- What about DHCP, DNS, TCP, UDP, HTTP and so on...
At the CCNA level you learn about filtering traffic with ACL's, but you only use Layer 3 IP ACLs. What about Layer 2 Mac ACLs? Do they exist? What would you use them for? If you don't understand the 7 layers you probably don't know, or even care at this point. And taking it one further, look up Flexible Packet Matching (FPM). If you neglect your CCNA basics, by the time you get to FPM you're going to struggle.
Food For Thought
To me, if you're going to be in this business you want to know these things. The basics are part of the game and you wouldnt want to skip over them just to get in there and take a test, get a certificate, and move on to the next exam. If that's the kind of person you are now, you might want to read my post "You Might Not Belong In IT." because this might be the slippery slope you're headed down. And if that's what your future looks like then I don't want to be the one cleaning up after you, and I'm sure there are thousands of other Networking guys like me that feel the same way.
Be in IT because you love it. Get Cisco certifications as a badge of honor that you could prove what you know, not because you can memorize a brain dump and bypass the funamental knowledge that these certiifcation programs are designed to instill in you.
Keep asking "Why?" If you can do that, and strive to find the answers, you'll probably end up a good engineer.