Subnet mask

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Subnet mask

Name:
Date:
Class:
A

Quick Questions

Shade in the A or B circle for each question.

1. A subnet mask such as 255.255.255.0 is used to...
A Split an IP address into a network part and a device (host) part
B Hide an IP address from other devices
2. Which one is written like a subnet mask?
A 255-255-255-0
B 255.255.255.0
3. With the mask 255.255.255.0, which part of the address 192.168.1.25 is the network part?
A 192.168.1
B 25
4. With the mask 255.255.255.0, which part of 192.168.1.25 is the device (host) part?
A 192.168
B 25
5. At a LAN party, your PC is 192.168.1.10 and your friend's PC is 192.168.1.20, both with mask 255.255.255.0. Are they on the same network?
A Yes, both have the network part 192.168.1
B No, because the last groups are different
B

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left columnRight column
1255.255.255.0 AThe network part is 192.168.1 and the device (host) part is 25
2192.168.1.25 with mask 255.255.255.0 BA subnet mask: the first three groups of an IP address name the network and the last group names the device
3A subnet mask is written in the same dotted format as an IP address: four groups of numbers separated by dots CA subnet mask needs four groups like an IP address. This one is missing the last group and should be 255.255.255.0.
4At a LAN party, two laptops on the same network share the same network part, so their first three groups match under mask 255.255.255.0 D255.255.255.0
5Mask 255.255.255.0: network part of 192.168.1.25 is 25 EThe network part is the first three groups (192.168.1), not the last group. The last group, 25, is the device (host) part.
6Subnet mask: 255.255.255 F192.168.1.10 and 192.168.1.11
C

Definitions

subnet mask
D

Fill in the Blanks

Complete each line of code by filling in the missing parts.

1.
IP address: 192.168.1.20 Subnet mask: _____________
2.
IP: 192.168.1.20 Mask: 255.255.255.0 Network part: _________
3.
IP: 192.168.1.20 Mask: 255.255.255.0 Host part: __
4.
PC1 IP: 192.168.1.10 PC2 IP: 192.168.1.11 Mask: 255.255.255.0 Same _______ part: 192.168.1
5.
IP address: 192.168.1.20 Mask: 255.255.___.0
E

Spot the Error

Shade in the letter of the line that contains an error.

Question 1
A # LAN Party network
B mask = 255.255.255
C ip = 192.168.1.20
Question 2
A ip = 192.168.1.20
B mask = 255.255.255.0
C network = 192.168.1
D host = 192
Question 3
A ip = 192.168.5.7
B mask = 255.255.255.0
C network = 192.168
D host = 7
Question 4
A mask = 255,255,255,0
B ip = 10.0.0.15
C network = 10.0.0
Question 5
A # Same network check
B pcA = 192.168.2.10
C pcB = 192.168.1.25
D mask = 255.255.255.0
E same = true

Answer Key

Subnet mask
Section A: Quick Questions
Q1
A — Split an IP address into a network part and a device (host) part
Q2
B — 255.255.255.0
Q3
A — 192.168.1
Q4
B — 25
Q5
A — Yes, both have the network part 192.168.1
Section B: Match the Pairs
Q1
255.255.255.0 → A subnet mask: the first three groups of an IP address name the network and the last group names the device
Q2
192.168.1.25 with mask 255.255.255.0 → The network part is 192.168.1 and the device (host) part is 25
Q3
A subnet mask is written in the same dotted format as an IP address: four groups of numbers separated by dots → 255.255.255.0
Q4
At a LAN party, two laptops on the same network share the same network part, so their first three groups match under mask 255.255.255.0 → 192.168.1.10 and 192.168.1.11
Q5
Mask 255.255.255.0: network part of 192.168.1.25 is 25 → The network part is the first three groups (192.168.1), not the last group. The last group, 25, is the device (host) part.
Q6
Subnet mask: 255.255.255 → A subnet mask needs four groups like an IP address. This one is missing the last group and should be 255.255.255.0.
Section C: Definitions
Q1
subnet mask — A number like 255.255.255.0 that splits an IP address into a network part and a device (host) part. With 255.255.255.0, the first three groups name the network.
Section D: Fill in the Blanks
Q1
IP address: 192.168.1.20 Subnet mask: 255.255.255.0
Q2
IP: 192.168.1.20 Mask: 255.255.255.0 Network part: 192.168.1
Q3
IP: 192.168.1.20 Mask: 255.255.255.0 Host part: 20
Q4
PC1 IP: 192.168.1.10 PC2 IP: 192.168.1.11 Mask: 255.255.255.0 Same network part: 192.168.1
Q5
IP address: 192.168.1.20 Mask: 255.255.255.0
Section E: Spot the Error
Q1
B — A subnet mask is written like an IP address, with four groups separated by dots. It should be mask = 255.255.255.0.
Q2
D — With the mask 255.255.255.0 only the last group is the device (host) part. The host is 20, not 192, which is part of the network.
Q3
C — The mask 255.255.255.0 makes the first three groups the network part. The network is 192.168.5, not just 192.168.
Q4
A — A subnet mask uses the same dotted format as an IP address, with dots between groups, not commas. It should be mask = 255.255.255.0.
Q5
B — With mask 255.255.255.0 the first three groups must match for the PCs to share a network. pcA has network 192.168.2 but pcB has 192.168.1, so same = true is wrong. pcA should be 192.168.1.10.