Currently, I am enrolled in a CCNA (Cisco Certified Network Associate) Certification Training Course here in Cebu City, in preparation of course for the CCNA Exam. One major topic discussed here is the IP (Internet Protocol) addressing, an interesting topic under data communication technology. IP address is assigned to a specified client (device) in a network for its identity and is presented in 32-bit (IPv4) with 4 octets separated by a period, for example: 10111001.00010010.11110001.10100011 or represented as 185.18.241.163 in decimal.
So, when discussing about this certain topic, you will encounter the words Classful & Classless IP addressing. What then is the difference between the two?
Classful IP - also known as the conventional IP addressing, is basically IP addresses classified under a Class with a given range and a default mask.
For the range, we have the following table:
| Class | Starting
Bits |
Decimal Range of First Byte | Network
Bits n bits |
Host Bits p bits |
Max
Networks 2n-m |
Max
Hosts 2p-2 |
| A | 0 (m-1) | 1 to 126 | 8 | 24 | 28-1 = 126 | 224-2= 16,777,214 |
| B | 10 (m=2) | 128 to 191 | 16 | 16 | 216-2 = 16,384 | 216-2=65,534 |
| C | 110 (m=3) | 192 to 223 | 24 | 8 | 224-3 = 2,097,152 | 28-2=254 |
| D | 1110 | 224 to 239 | ||||
| E | 1111 | 240 to 254 |
Commonly, we only use Class A, B & C since Class D & E are for multicasting and experimental purposes respectively. By the way, notice that 127 is not included in the range because it is assigned for loopback, usually assigned to your localhost or your PC.
For its subnet mask:
| Network address range | Default mask |
| Class A - 10.0.0.0 – 10.255.255.255 | 255.0.0.0 |
| Class B - 172.16.0.0 – 172.31.255.255 | 255.255.0.0 |
| Class C – 192.168.0.0 – 192.168.255.255 | 255.255.255.0 |
So, for example, if you check your IP address using ipconfig, and shows you with IP address 192.168.2.100 and subnet mask of 255.255.255.0 — that means you’re under a Class C network. Click here for online Classful IP Calculator tool if you need help.
Classless IP – as defined by its name, it does not follow any Class as above. When you encounter and IP address with a subnet mask which is not 255.0.0.0 or 255.255.0.0 nor 255.255.255.0 that means that it’s a classless IP.
I am not really an expert on this topic, but if you need to understand more in details about this, you can check this site.
Hi Jerome. Thank you for sharing this. I wonder how does this work though on Facebook. For example, I tried their SMS notification service. Supposedly, it should not send me an SMS if I am online – but it still does (which prompted me to deactivate it.
When I shared this in my status and referring to it as some kind of bug, someone remarked as being online gives you a “stateless” IP therefore it can’t distinguish.
Not sure if that question can be related to this topic. Thanks again!