How should I use these Subnetting practice questions?

Read each scenario carefully and choose your answer before revealing the explanation. Then check why your choice was right or wrong. Repeat until the reasoning feels automatic.

Can I practise just Subnetting questions in a focused session?

Yes — use the session launcher on this page to start a 10-, 20-, 30- or 50-question session drawn entirely from the Subnetting domain.

200-301 · topic practice

Subnetting practice questions

Practise 200-301 subnetting questions covering CIDR notation, subnet mask conversion, network and broadcast address calculation, usable host ranges, and determining which subnet a device belongs to.

Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.

Reviewed byJohnson Ajibi· MSc IT Security

20 questionsDomain: Subnetting

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What the exam tests

What to know about Subnetting

Subnetting questions test whether you can calculate network ranges, usable hosts, masks, prefixes and the correct subnet for a device.

CIDR notation and subnet mask conversion.

Network, broadcast and usable host ranges.

How many hosts or subnets are required.

Which subnet a given IP address belongs to.

Why learners struggle

Why Subnetting questions are commonly missed

Subnetting questions are missed when learners calculate the right subnet size but pick the wrong network address, forget to subtract network and broadcast addresses from usable hosts, or confuse the number of subnets with the number of hosts per subnet.

·Network and broadcast are not usable — subtract 2 from the host count for every subnet
·Block size — always a power of 2; 2^host-bits gives addresses per subnet
·Which subnet a host is in — divide the host octet by block size to find the network address
·Subnets vs hosts per subnet — different calculations that learners frequently swap
·CIDR prefix vs subnet mask — /24 = 255.255.255.0, /25 = 255.255.255.128
·A valid mask does not mean it meets the design requirement — check the host count

Watch out for

Common Subnetting exam traps

▸Network and broadcast addresses are not usable host addresses in normal IPv4 subnets.
▸Subnets and hosts per subnet are different calculations.
▸The prefix length must be checked against the block size.
▸A mathematically valid mask may still fail the design requirement.

Practice set

Subnetting questions

20 questions · select your answer, then reveal the explanation

Question 1hardScenario

Study the full IPv6 explanation →

You are connected to R1. Configure IPv4 and IPv6 addressing on R1's interfaces and verify reachability to R2. The current configuration has a wrong subnet mask on G0/0, missing default gateway for IPv4, and R1's IPv6 address is configured using EUI-64 while R2 uses a static IPv6 address. Fix these issues so that R1 can ping both R2's IPv4 and IPv6 addresses.

Exhibit

R1#show running-config
Building configuration...

hostname R1
!
interface GigabitEthernet0/0
 ip address 192.0.2.1 255.255.255.0
 ipv6 address 2001:db8:1::/64 eui-64
 no shutdown
!
interface GigabitEthernet0/1
 ip address 198.51.100.1 255.255.255.0
 ipv6 address 2001:db8:2::1/64
 no shutdown
!
ip route 0.0.0.0 0.0.0.0 192.0.2.254
!
end

R2#show running-config
Building configuration...

hostname R2
!
interface GigabitEthernet0/0
 ip address 192.0.2.2 255.255.255.252
 ipv6 address 2001:db8:1::2/64
 no shutdown
!
interface GigabitEthernet0/1
 ip address 203.0.113.1 255.255.255.0
 no shutdown
!
end

R1#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0     192.0.2.1       YES manual up                    up
GigabitEthernet0/1     198.51.100.1    YES manual up                    up

R1#ping 192.0.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

R1#ping 2001:db8:1::2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:db8:1::2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Trap 1: Change R1 G0/0 subnet mask to /30, add a default route via…

This is incorrect because the default route points to 192.0.2.254, which is not R2's G0/0 IP (192.0.2.2), so IPv4 traffic will not be forwarded. Also, EUI-64 generates an interface ID from the MAC, which will not match the subnet expected by R2's static address 2001:db8:1::2/64.

Trap 2: Change R1 G0/0 subnet mask to /24, add a default route via…

This is incorrect because the subnet mask on R1's G0/0 remains /24, which does not match R2's /30. R1 will consider the subnet to be 192.0.2.0/24, while R2 uses 192.0.2.0/30, causing a mismatch that prevents direct communication.

Trap 3: Change R1 G0/0 subnet mask to /30, add a default route via…

This is incorrect because while the IPv4 issues are fixed, the IPv6 address generated by EUI-64 will not match the subnet expected by R2's static address 2001:db8:1::2/64. EUI-64 creates an interface ID based on the MAC, which is unpredictable and unlikely to be in the same subnet as R2's static address.

Study all Subnetting common traps →

A
Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.2, and configure a static IPv6 address 2001:db8:1::1/64 on G0/0.
This corrects all three issues: the mask matches R2's /30, the default route points to R2's G0/0 IP (192.0.2.2), and the static IPv6 address places R1 on the same subnet as R2's static address 2001:db8:1::2/64.
B
Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.254, and keep the EUI-64 IPv6 address on G0/0.
Why wrong: This is incorrect because the default route points to 192.0.2.254, which is not R2's G0/0 IP (192.0.2.2), so IPv4 traffic will not be forwarded. Also, EUI-64 generates an interface ID from the MAC, which will not match the subnet expected by R2's static address 2001:db8:1::2/64.
C
Change R1 G0/0 subnet mask to /24, add a default route via 192.0.2.2, and configure a static IPv6 address 2001:db8:1::1/64 on G0/0.
Why wrong: This is incorrect because the subnet mask on R1's G0/0 remains /24, which does not match R2's /30. R1 will consider the subnet to be 192.0.2.0/24, while R2 uses 192.0.2.0/30, causing a mismatch that prevents direct communication.
D
Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.2, and keep the EUI-64 IPv6 address on G0/0.
Why wrong: This is incorrect because while the IPv4 issues are fixed, the IPv6 address generated by EUI-64 will not match the subnet expected by R2's static address 2001:db8:1::2/64. EUI-64 creates an interface ID based on the MAC, which is unpredictable and unlikely to be in the same subnet as R2's static address.

Subnetting practice questions

What to know about Subnetting

Why Subnetting questions are commonly missed

Common Subnetting exam traps

Subnetting questions

Exhibit

Which three of the following are correct steps in the process of CDP (Cisco Discovery Protocol) neighbor discovery? (Choose three.)

Exhibit

Exhibit

Which TWO commands or tools would a network engineer use to verify if a client has a duplicate IP address conflict on the local subnet?

Drag and drop the following steps into the correct order to configure a Cisco IOS-XE router as a DHCP relay agent and verify the DHCP DORA process for a client on a different subnet.

A host sends traffic to a web server on another subnet. Which address is used as the destination MAC address in the first Ethernet frame sent by the host?

A router interface is configured with 192.0.2.97/28. What is the network address of the subnet?

A client connects to an employee WLAN using 802.1X authentication. The authentication process completes successfully, but the client fails to obtain an IP address via DHCP. What is the most likely cause?

Exhibit

An OSPF-enabled router R1 fails to advertise the 192.168.50.0/24 network to neighbor R2, even though the neighbor relationship is up. Which misconfiguration on R1 would cause this?

Exhibit

A subnet uses the mask 255.255.255.224. How many usable host addresses does it provide?

A host with address 192.168.1.130/26 needs to identify its local subnet. Which subnet does it belong to?

A host has the address 10.10.10.94/27. Which subnet contains that host?

A subnet must support 14 usable hosts. Which prefix is the smallest that meets the requirement?

A host with address 172.16.5.10/23 wants to determine whether 172.16.6.20 is on the same local network. What is the correct conclusion?

A host is configured with IP address 172.16.100.222/27. Which address is the broadcast address for its subnet?

A subnet requires 200 usable host addresses. Which prefix is the smallest that meets the requirement?

R1 and R2 are connected via a GigabitEthernet link in the same IPv4 subnet, and both routers have OSPF configured in the same area. However, R1 is not learning any OSPF routes from R2. What is the most likely cause?

Exhibit

A host is configured with 10.10.10.130/25. What is the network address of its subnet?

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