1.7 Classful Subnetting

Question 1

What does a Class A IP address represent in terms of network and host bits?

Answer 1

Class A address has 8 bits for the network and 24 bits for the host. Its default subnet mask is 255.0.0.0.

Transcript: “Anything that is a class A address has eight bits assigned for the network address and 24 bits that are associated with the host address.” (0:21–0:27)

Question 2

What is the default subnet mask for Class B IP addresses and how are the bits divided?

Answer 2

Class B has 16 bits for the network and 16 bits for the host. The default subnet mask is 255.255.0.0.

Transcript: “A class B address default subnet mask is 255.255.0.0.” (0:37–0:42)

Question 3

Describe the structure of a Class C IP address.

Answer 3

Class C uses 24 bits for the network and 8 bits for the host. The default subnet mask is 255.255.255.0.

Transcript: “And the default subnet mask for a class C address is 255.255.255.0.” (0:45–0:49)

Question 4

Why do we still refer to IP classes even though class-based subnetting is no longer used?

Answer 4

Classes serve as starting points for subnetting, helping to define where the network portion ends and host portion begins.

Transcript: “That’s because these classes do act as a starting point when we begin any type of subnetting on our networks.” (1:16–1:20)

Question 5

How can you determine the class of an IP address by its first octet?

Answer 5

0–127 = Class A

128–191 = Class B

192–223 = Class C

Transcript: “If the decimal octet is between 0 and 127… it’s a class A… 128 and 191… class B… 192 and 223… class C.” (2:30–2:48)

Question 6

Which IP address classes are reserved for special purposes?

Answer 6

Class D (224–239) is used for multicast. Class E (240–255) is reserved and not used for standard addressing.

Transcript: “Class D addresses are used for multicast communication… Class E range… not used for any purpose.” (3:04–3:31)

Question 7

What are the four critical values in IP subnetting?

Answer 7

Network address, first usable host address, broadcast address, last usable host address.

Transcript: “There are four different values that are very important to know…” (4:57–5:01)

Question 8

How do you calculate the network address of a subnet?

Answer 8

The first IP address of a subnet. Set all the host bits to 0 based on the subnet mask (0 decimal)

Transcript: “To calculate a network address, you set all of the host bits of that address to 0…” (5:12–5:15)

Question 9

How do you determine the broadcast address for a subnet?

Answer 9

The last IP address of a subnet. Set all host bits to 1, then convert to decimal. (255 decimal)

Transcript: “To calculate the network broadcast address, you would set all of your host bits to 1…” (5:43–5:45)

Question 10

Given IP 10.74.222.11 (Class A), what are the subnet values? (Network address, first host, broadcast, last host)

Answer 10

Network Address: 10.0.0.0

First Host: 10.0.0.1

Broadcast: 10.255.255.255

Last Host: 10.255.255.254

“So the last usable address on this network is 10.255.255.254.” (7:36–7:42)

Question 11

For IP 172.16.88.200 (Class B), what are the subnet values? (Network address, first host, broadcast, last host)

Answer 11

Network Address: 172.16.0.0

First Host: 172.16.0.1

Broadcast: 172.16.255.255

Last Host: 172.16.255.254

Transcript: “…the last usable address is 172.16.255.254.” (9:06–9:13)

Question 12

For IP 192.168.4.77 (Class C), what are the subnet values? (Network address, first host, broadcast, last host)

Answer 12

Network Address: 192.168.4.0

First Host: 192.168.4.1

Broadcast: 192.168.4.255

Last Host: 192.168.4.254

“…that would be 192.168.4.254.” (10:20–10:27)

Question 13

How do you calculate the first usable host address of a subnet?

Answer 13

Know the network address; add one to the network address to get the first usable host address

Question 14

How do you calculate the last usable host address of a subnet?

Answer 14

Know the broadcast address; subtract one to get the last usable host address