ICND1 Subnetting 3 — Questions and Answers
Question 1: What is the valid host range for the subnet 172.30.4.0/22?
- 172.30.4.1 – 172.30.7.254 (Correct answer)
- 172.30.4.1 – 172.30.4.254
- 172.30.4.1 – 172.30.5.254
- 172.30.4.1 – 172.30.6.255
Correct answer: 172.30.4.1 – 172.30.7.254
A /22 block spans 1024 addresses; 172.30.4.0 to 172.30.7.255, so valid hosts are .4.1 through .7.254.
Question 2: Which CIDR prefix provides exactly 510 usable host addresses?
- /23 (Correct answer)
- /22
- /24
- /21
Correct answer: /23
A /23 has 512 total addresses (2^9), minus 2 equals 510 usable hosts.
Question 3: A host has the IP address 10.10.16.55 with a mask of 255.255.252.0. What is its subnet's broadcast address?
- 10.10.19.255 (Correct answer)
- 10.10.16.255
- 10.10.17.255
- 10.10.23.255
Correct answer: 10.10.19.255
255.255.252.0 is /22; the block of 4 in the third octet containing 16 is 16–19, so broadcast is 10.10.19.255.
Question 4: In VLSM design, which benefit does it provide over classful subnetting?
- Allows different subnet sizes within the same network (Correct answer)
- Eliminates the need for a default gateway
- Allows more than 254 subnets per class C
- Automatically assigns IP addresses to hosts
Correct answer: Allows different subnet sizes within the same network
VLSM lets you apply different prefix lengths to different subnets, reducing address waste.
Question 5: What is the subnet mask in dotted-decimal notation for /19?
- 255.255.224.0 (Correct answer)
- 255.255.240.0
- 255.255.248.0
- 255.255.192.0
Correct answer: 255.255.224.0
/19 sets 19 bits; the third octet has top 3 bits set: 11100000 = 224, giving 255.255.224.0.
Question 6: How many total IP addresses (including network and broadcast) does a /29 subnet contain?
- 8 (Correct answer)
- 6
- 16
- 32
Correct answer: 8
A /29 has 32 - 29 = 3 host bits, so 2^3 = 8 total addresses.
Question 7: An engineer needs to connect two routers with a point-to-point link using the fewest IP addresses. Which subnet should be used?
- /30 (Correct answer)
- /29
- /28
- /31
Correct answer: /30
A /30 provides 4 addresses (2 usable), which is the traditional minimum for a point-to-point link per ICND1 objectives.
ICND1 Subnetting 3
What is the valid host range for the subnet 172.30.4.0/22?