In this video, Bill Ferguson explains Class C addresses, and why the first two bits are always set to 1 and the third bit is set to 0. Examine the effect of this setting on the rest of the IP addressing structure.
- [Instructor] What about those companies that just needed…a couple of hundred hosts?…Well, the original designers had a plan…in mind for them as well.…So the standard that they developed included…that the first bit in the first octet must be on,…the second bit must be on,…and the third bit must be off.…That means that the first bit, a 128th, has value.…The second bit has value as well, and that's a 64.…
Add those together you get 192.…Then the third bit has to be off.…That means that if we add the rest of the five bits…that are in the first octet together,…the highest that we can get is to 223.…So 192 to 223 would be the first octet number…for a Class C address.…But the standard also included…that the subnet mask must be changed…to 255.255.255.0.…
That means that the subnet mask would have 24 ones…followed by eight zeros.…That can also be expressed as a /24.…So what does that do for us…as far as networks are concerned?…Well, we can have two to the 21st networks.…Why is that?…Well, we have 24 bits that can be used…
Discover how IP addresses are constructed and how to understand them better by relating them to a picture rather than converting binary numbers or memorizing charts. Learn the benefits that subnetting in your head provides in every aspect of IT networking, including routing protocols, access control lists, and network address translation. Then walk through Bill's four-step method, which leverages the rules that were used to create the original classful IP addressing schemes. Using this method, students can learn to "see" the IP addresses for each subnet. Watch the technique in action, and then practice what you've learned using the audio guides in chapter five, which provide auditory cues as you subnet in your head.
- The benefits of subnetting
- Class A, B, and C IP addressing
- The four-step subnetting method
- Troubleshooting IP topologies and IP host address ranges
- Audio cues for the four-step method