Want to discuss this topics long long time ago, that is the subnet calculation. As I find that many students are not really know how to find the subnet address of an given IP for non-byte boundary subnet mask such as /27, /19 etc.

That's understandable, as all the formal training (like CCNA) teaches how to do the calculation in binary, but who would like to deal with those 0's and 1's? Probably, nobody. So when I teach CCNA, I will teach them how to use decimal for the calculation. Especially, when you take the CCNA examination, no calculator (not to mention your mobile phone) is allowed, you need to do it by hand. Thus, you really need to learn a more effective way for those calculation.

I've just created two youtube videos for the subnet calculation using decimal in Part 1 and Part 2. Part 1 will focus the basic technique for Class C network number and how to tackle one of the common question in the examination. While Part 2 discusses more common questions and the case for Class B and Class A network number.

In fact, its just like cutting a cake. E.g. following illustrate the case of /27 subnets

In the recent Cisco training courses, the whole certification track has been revised.  For the CCNA course, personally I really think that it's no longer an introductory course (even for the previous version). As new topics that originally from other specialized training has been added into the course. Somewhat like SDN, wireless controller, those are no longer basic network technologies.

Of course, the key topics are still routing and switch. Yet, EIGRP has been taken out. The new version only discuss OSPF. As there are so many topics to discuss, obvious the course pace will be quite fast. If you are completely new to network, it's not easy to catch up.

What I recommend (that's I already recommend 10 years ago!), before you attend the class, you should at least get some basic knowledge about switch and router, how they works in the network. Recently, I've created a youtube video CCNA Pre-class to help you getting the fundamental concepts. Even if you have been working in networking field for a short period of time, this video can help you clear all the basic concepts.

Besides, if you are new to Cisco equipment, try download some simulator (something like GNS3) and practice the basic command line interface before you attend the class.