For individuals looking to delve into the complex world of networking, the word subnetting will most certainly inspire a cringe. It has been my experience, that the single most difficult concept for people to understand is why we subnet. Everyone knows that old line about running out of IP address, but the wide scale use of NAT and PAT, along with the private address space, running out of IP addresses seams less likely.
The key word is seams. Before the days of CIDR (Classless Inter-Domain Routing) all IP address were broken down into classful boundaries. That meant that the smallest network that could be assigned was a class C, consisting of 254 usable IP addresses. Every ISP would be required to assigned 254 IP address for every client, even for a home user that may only have 1 computer. This is regardless of NAT.
What You Need to Know
When it comes to subnetting, you should be able to do three things.
- You must be able to determine how many networks, of a given size, you can fit into a large, given, network.
- You must be able to determine that Network ID and Broadcast Address of a given IP address and Subnet Mask.
- You must be able to break down, or subnet, a large network into smaller networks of varying sizes.
Breaking it Down
By far the easiest of the three is the first one. When given a network, say 192.168.0.0/24, you must be able to determine how many smaller networks, say a /27, the large network can yield. What makes the first the easiest, is the fact that you use one simple formula.
Using the above example, we want to determine ho many smaller networks can be derived from the larger network. The answer is simple.
2(27-24) = 23 = 8
Stay Tuned...More to Come
Sebastian Abbinanti, CCNA
At MicroTrain we've been preaching the value of using social media in your job search. Of course it is a relatively common theme in the job search community, with the proliferation of social media it is only natural to try to use it to your advantage.
But does it really help? To answer that, let me tell a quick story.
I have a good friend who lives in Milwaukee, and who is unfortunately someone I don't talk to nearly enough. A few weeks ago I saw that he had posted on his Facebook page that due to his company's recent merger his job was being eliminated. Always rough, but with his 3 month old baby and unemployment at 10%, that is especially brutal. Of course everyone posted comments on his Facebook page saying how sorry they were, but as the old saying goes 'sorry don't feed the bulldog' .
After offering my condolences, I asked him what kind of job he was looking. He said he was looking for a marketing position, with an emphasis on project management and then shot me over a PDF of his resume that I would share should the need arise. I told him I'd keep my eyes and ears open and see what comes up in my network of contacts.
Fast forward to the other day, when I received my weekly Linked In email update. Normally this is a quick read, as I just browse to see who has gotten new jobs, promotions, or connected with people that I may want to add to my network. But this week, I saw that one of my contacts who also happens to be in Milwaukee, posted that she is looking for a marketing professional with project management experience. Small world indeed. So I sent her an email, told her the story and attached my friend's resume. She responded immediately, saying that on paper he looks perfect and that she would touch base with him right away. I asked him how it went, and he confirmed that he has an interview scheduled for Friday.
Now of course he may not actually get the job - interviewing is a whole other part of the job search process. But clearly social networking helped him even find this opportunity. Without his Facebook notice I wouldn't have known he was looking for work. And without my other friend's comment on Linked In I wouldn't have known that she was looking to fill this position. Multiply that by the hundreds of people you have in your network, and its pretty easy to see how it can lead to some opportunities that may not have been there otherwise when you use social media effectively in your job search.