CCST Subnetting and CIDR Notation 2 — Questions and Answers
Question 1: A company needs 5 subnets with at least 25 hosts each. Which subnet mask is most appropriate?
- /27 (Correct answer)
- /28
- /29
- /26
Correct answer: /27
A /27 subnet provides 30 usable host addresses (2^5-2), which meets the requirement of at least 25 hosts per subnet.
Question 2: What is the total number of IP addresses (including network and broadcast) in a /29 subnet?
- 8 (Correct answer)
- 6
- 16
- 4
Correct answer: 8
A /29 subnet has 3 host bits (32-29=3), giving 2^3=8 total addresses including the network and broadcast addresses.
Question 3: Which statement best describes Variable Length Subnet Masking (VLSM)?
- All subnets must be the same size
- Different subnets can use different prefix lengths based on requirements (Correct answer)
- VLSM only applies to Class A addresses
- VLSM requires all subnets to use the same prefix length
Correct answer: Different subnets can use different prefix lengths based on requirements
VLSM allows network designers to allocate subnets of different sizes, using the appropriate prefix length for each subnet based on the number of hosts needed.
Question 4: What is the dotted-decimal subnet mask for the /20 prefix length?
- 255.255.240.0 (Correct answer)
- 255.255.248.0
- 255.255.224.0
- 255.255.252.0
Correct answer: 255.255.240.0
A /20 mask has 20 ones: the first two octets are 255.255, and the third octet has 4 ones (11110000 = 240), giving 255.255.240.0.
Question 5: How many subnets can be created by borrowing 3 bits from the host portion of a subnet?
- 6
- 8 (Correct answer)
- 4
- 16
Correct answer: 8
Borrowing 3 bits creates 2^3=8 subnets, as each additional borrowed bit doubles the number of available subnets.
Question 6: What is the valid host range for the network 172.16.0.0/16?
- 172.0.0.1 to 172.255.255.254
- 172.16.0.1 to 172.16.255.254 (Correct answer)
- 172.16.0.0 to 172.16.255.255
- 172.16.1.0 to 172.16.254.255
Correct answer: 172.16.0.1 to 172.16.255.254
For 172.16.0.0/16, the network address is 172.16.0.0 and broadcast is 172.16.255.255, so valid hosts range from 172.16.0.1 to 172.16.255.254.
Question 7: Which RFC defines the private IPv4 address ranges used in internal networks?
- RFC 1918 (Correct answer)
- RFC 2460
- RFC 1519
- RFC 793
Correct answer: RFC 1918
RFC 1918 defines three private IPv4 address ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, which are not routable on the public Internet.
CCST Subnetting and CIDR Notation 2
A company needs 5 subnets with at least 25 hosts each.
Which subnet mask is most appropriate?