IPv4 Address Classes Flashcards

Q: What is the FIRST thing you look at to determine an IP address's class?

A: The first octet (the first number).

Q: An IP starts with 10. What class is it?

A: Class A

Q: An IP starts with 172. What class is it?

A: Class B

Q: An IP starts with 192. What class is it?

A: Class C

Q: What class is 192.168.1.25?

A: Class C

Q: What class is 172.20.5.8?

A: Class B

Q: What class is 10.1.1.1?

A: Class A

Q: What first-octet range is Class A?

A: 1–126

Q: What first-octet range is Class B?

A: 128–191

Q: What first-octet range is Class C?

A: 192–223

Q: What is the default mask for Class A?

A: 255.0.0.0 (/8)

Q: What is the default mask for Class B?

A: 255.255.0.0 (/16)

Q: What is the default mask for Class C?

A: 255.255.255.0 (/24)

Q: How many 255s are in the default mask for Class A?

A: 1

Q: How many 255s are in the default mask for Class B?

A: 2

Q: How many 255s are in the default mask for Class C?

A: 3

Q: Which private IP range belongs to Class A?

A: 10.0.0.0–10.255.255.255

Q: Which private IP range belongs to Class B?

A: 172.16.0.0–172.31.255.255

Q: Which private IP range belongs to Class C?

A: 192.168.0.0–192.168.255.255

Q: Is 10.15.8.9 a private IP?

A: Yes (Class A private)

Q: Is 172.25.4.10 a private IP?

A: Yes (Class B private)

Q: Is 192.168.100.50 a private IP?

A: Yes (Class C private)

Q: What is 127.0.0.1?

A: Loopback (localhost)

Q: Why isn't 127.x.x.x used for normal devices?

A: It's reserved for loopback testing.

Q: What class is 8.8.8.8?

A: Class A

Q: What class is 150.10.20.30?

A: Class B

Q: What class is 200.10.5.1?

A: Class C

Q: Is every Class A address private?

A: No. Only 10.0.0.0/8 is private.

Q: Is every Class B address private?

A: No. Only 172.16.0.0–172.31.255.255 is private.

Q: Is every Class C address private?

A: No. Only 192.168.0.0/16 is private.