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200-301 · Question #21

Drag and Drop Question Drag and drop the IPv4 network subnets from the left onto the correct usable host ranges on the right Answer:

IPv4 Subnetting: Drag-and-Drop Explanation The core task: given a host address with a prefix length (e.g., 172.28.228.144/18), determine which network that address belongs to, then calculate the usable host range of that network. The same host IP (172.28.228.144) appears in all f

Submitted by tom_us· Mar 5, 2026Network Fundamentals

Question

Drag and Drop Question Drag and drop the IPv4 network subnets from the left onto the correct usable host ranges on the right Answer:

Exhibit

Explanation

IPv4 Subnetting: Drag-and-Drop Explanation

The core task: given a host address with a prefix length (e.g., 172.28.228.144/18), determine which network that address belongs to, then calculate the usable host range of that network.

The same host IP (172.28.228.144) appears in all five subnets - only the prefix length changes, which changes the network boundaries.

Key Formula

Network address = host IP AND subnet mask
Broadcast = network address OR (inverted mask)
Usable range = (network + 1) to (broadcast - 1)
Block size = 2^(32 - prefix)

Item-by-Item Breakdown

1. `172.28.228.144/18` -> `172.28.192.1 - 172.28.255.254`

Mask: 255.255.192.0; block size in 3rd octet = 64
228 AND 192 = 192 -> network = 172.28.192.0
Broadcast = 172.28.255.255 (192 + 64 - 1 = 255)
Usable: .192.1 -> .255.254

2. `172.28.228.144/21` -> `172.28.224.1 - 172.28.231.254`

Mask: 255.255.248.0; block size in 3rd octet = 8
228 AND 248 = 224 -> network = 172.28.224.0
Broadcast = 172.28.231.255 (224 + 8 - 1 = 231)
Usable: .224.1 -> .231.254

3. `172.28.228.144/23` -> `172.28.228.1 - 172.28.229.254`

Mask: 255.255.254.0; block size in 3rd octet = 2
228 AND 254 = 228 -> network = 172.28.228.0
Broadcast = 172.28.229.255 (228 + 2 - 1 = 229)
Usable: .228.1 -> .229.254

4. `172.28.228.144/25` -> `172.28.228.129 - 172.28.228.254`

Mask: 255.255.255.128; block size in 4th octet = 128
144 AND 128 = 128 -> network = 172.28.228.128
Broadcast = 172.28.228.255 (128 + 128 - 1 = 255)
Usable: .228.129 -> .228.254

5. `172.28.228.144/29` -> `172.28.228.145 - 172.28.228.150`

Mask: 255.255.255.248; block size in 4th octet = 8
144 AND 248 = 144 -> network = 172.28.228.144
Broadcast = 172.28.228.151 (144 + 8 - 1 = 151)
Usable: .228.145 -> .228.150

Pattern to Notice

The subnets nest inside each other - each smaller prefix (/18 -> /29) carves out a progressively smaller slice, all containing 172.28.228.144:

/18  172.28.192.0   ──────────────────────────────────────
/21  172.28.224.0             ────────────────
/23  172.28.228.0                    ──────
/25  172.28.228.128                    ───
/29  172.28.228.144                     ─

Common Mistakes

Mistake	Why it's wrong
Using `.144` as the network start for /25	144 AND 128 = 128, not 144 - the network starts at .128
Forgetting the /29 network is 172.28.228.144	Here the host address equals the network address; usable starts at .145
Confusing block size in 3rd vs 4th octet	For /18-/23, the variable bits span the 3rd octet; for /25-/29, they're in the 4th
Off-by-one on usable range	Network address and broadcast are not usable - always add 1 / subtract 1

Topics

#IPv4 Subnetting#CIDR Notation#Network Addressing#Host Range Calculation

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