I hate subnetting!

johnnynodough

Always have, always will.

I have dealt with subnetting on tests at least three times, with Net+ (not so much, MCSE 70-216 (quite a bit) and MCSE 70-221 (and some more). Each time I guess I remembered enough to pass, although I probably just bombed those parts and aced the rest.

I am determined to subnet like a SOB! Everything else is pie, subnetting is the only reason I have been pushing off CISCO for years.

So, please, post some help. I know there is just one little peice of information that someone could say that would flip on the light bulb for me, I am close. Already checked out learntosubnet.com.

Sorry if this is already on the board, I didnt bother to look to much as my brain really hurts from being rediculed by little 1's and 0's all day

wildfire

I must admit that subnetting is not my favourite topic either! and the CCNA exam hammers you on subnetting. Im affraid I couldnt find a quick fix! and the only was to practice and practice and what I did find helped was as soon as the exam started I wrote out all the subnet/number of hosts/networks etc on the thing they give you to make notes on. Evfery question then that involved subnetting simply meant looking down at my note and the answer was there.

I used this site when I was studying for CCNA http://www.silverdragon.com/punkie/howto/subnetting.html

kplab

You can find some practice questions on subnetting at:

http://www.celticrover.com

Munck

I learned to subnet using Todd Lammle's 5th edition CCNA study guide. Very well and easy to understand laid out. Took me 3 days. Recommended.

Drakonblayde

Honestly, once it clicks, subnetting is one of the things you'll find easiest in the Cisco world. But getting it to click can be a royal pain in the behind hehe

sputnic68

Drakonblayde is right, it's a pain in the butt to remember but when it clicks it stays in your head. Once you'll get it, you won't believe how easy it is. One thing you must have on the tip of your tongue is the different masks or prefex lengths. You'll use these in an everyday work environment with networks.

Webmaster

I also agree with Drakonblayde. Although VLSM and CIDR, supernetting etc, can make it more difficult in large networks, it is one of the easier topics for Cisco. It's 'only' the addressing scheme, making sure the addresses are valid and known throughout a network as well as allowing communication between the entities that have an address is where it becomes harder.

Always have, always will.

Well, if you need it in real-world scenarios you will eventually remember them, know them by heart, especially the common ones, because you either calculated them manually or by using a subnet calculator that many times.

Here are some other subnet resources that may be helpful:
www.learntosubnet.com
www.mcmcse.com/articles/subnetting123.shtml

johnnynodough

WOw, I found a really good ebook on this, I actually even payed for it, which is pretty rare for me. It took me back to the basics and brought me back up, and in the middle I got those little peices that I was missing. Still not subnetting like an SOB, but I am doing it and I actually fully understand what I am doing for a change, now I just need to keep on the practice so I can do it faster.

http://www.thebryantadvantage.com/TheBryantAdvantageMasterySeries.html

rong

I can sympathize with you. I have no where near the certs that you hold, but with my job one of the features with these systems is to run on it's own subnet. Every once in a while I will run into a Network administrator, who is not happy about adding more devices to his/her network and will give the least amount of support to me. Long story short, I had to learn subnetting basically on my own. I earned A+ & Net+ and thought that that would be good enough. WRONG! I finaly took the CCNA training and that's when it clicked. It helped a lot that one of the diagnostic tools that I have for these access systems allows you to read data between the controller and the host in either decimal, hex, or binary; so I already knew how to read binary and count in binary.

I have used a subnet calculator, BUT IT WASN'T A VERY GOOD ONE. Now I always do subnetting on paper & shoot a copy to my corporate Network Administrator (who is a CCIE) for verification. He's never found an error. My advise to you is to just simply practice, practice, practice, and whatever you do DO NOT USE A CALCULATOR! Always use paper for subnetting!

johnnynodough

This is amazing, I can do this in my head now very fast and I actually understand what I am doing. Just that one little pice of info made the difference. I again recommend that link I posted to anyone who is battling this

Nocturnal

What part of it is difficult for you? Is it the CIDR notation? You need to pretty much memorize some sequences. First, remember this one:

128,192,224,240,248,252,254,255

The binary equivalents of them are:

10000000, 11000000, 11100000, 11110000, 11111000, 11111100, 11111110, and of course, 11111111

Those are the only numbers you'll ever see in a subnet mask, and notice that there are eight of them. Then there this sequence:

128,64,32,16,8,4,2,1

There are eight of those too.

Remember the major network boundaries, /8, /16, and /24.

If you have a /30, that's a /24 + 6. Notice that the sixth number in the first sequence is 252, or 11111100. The /30 is your basic netmask for a point to point connection.

If you have a /20, that's a /16 +4. That's 240 or 11110000. OH MAN...how many hosts is that? Simple, you know there are 256 (-2) in a /24, now just double it four times, 512, 1024, 2048, 4096. Subtract two and there you are.

If you toss out a subnetting question, I'll pick it apart for you and share how I do it. I do a lot of work with /20-something blocks.

Like people say, once you get it down, you'll be wondering why it took you so long to figure it out.

Just for laughs, here's another sequence:

255,127,63,31,15,7,3,1

11111111, 01111111, 00111111, 00011111, 00001111, 00000111, 00000011, 00000001

That's the pattern for wildcard masks. Just get the first and second sequence down and this one will follow naturally.

You just have to play around with it and commit the patterns to memory. Hope this helps.