CCNA DC FAQ: Anayzing Classful IPv4 Networks Figure: Numbers and Sizes of Class A, B, and C Networks Q1. Which of the following are not valid Class A network IDs? (Choose two answers.) a. 1.0.0.0 b. 130.0.0.0 c. 127.0.0.0 d. 9.0.0.0 Answer: B and C. Class A networks have a first octet in the range of 1–126, inclusive, and their network IDs have a 0 in the last three … [Read more...]