I was watching a tutorial video on Lynda.com. The presenter said:
- Class A: First octet between 1 and 126.
- Class B: First octet between 128 and 191.
- Class C: First octet between 192 and 223.
I did some Google searching, and according to Wikipedia,
- Class A starts from 0.0.0.0 and ends with 127.255.255.255.
- Class B starts from 22.214.171.124 and ends with 126.96.36.199.
- Class C starts from 192.0.0.0 and ends with 188.8.131.52.
- Class D starts from 184.108.40.206 and ends with 220.127.116.11.
- Class E starts from 240.0.0.0 and ends with 255.255.255.255.
I found another similar course on Udemy. The presenter said:
- Class Address Range
- A 18.104.22.168 to 22.214.171.124
- B 126.96.36.199 to 188.8.131.52
- C 184.108.40.206 to 220.127.116.11
- D 18.104.22.168 to 22.214.171.124
- E 240.0.0.0 to 254.255.255.254
I cannot ask the presenters directly, so my questions are:
- Should 127 be included in Class A or not?
- Why does the address range vary (sometimes from 126.96.36.199, sometimes from 188.8.131.52, as well as end with 254 or 255)? Which one is correct?
I am surprised that this classful addressing must have been around for years, why there is not a unified definition? Sorry about the wordy questions and thanks in advance.