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IPv4 Subnetting Practice Flashcards: Boundaries & Host Ranges

48 original IPv4 subnetting flashcards on network and broadcast boundaries, usable host endpoints, address roles, capacity, and common mistakes, with brief worked reasoning.

By author Open Study Contributor

About this deck

Practice IPv4 subnetting with 48 original English flashcards. Each card asks for one result: a CIDR subnet mask or count, a network or broadcast address, a usable host-range endpoint, an address role, a numerical same-subnet decision, a capacity prefix, or one corrected value in a subnetting mistake. Two inverse cards retrieve a unique prefix from a mask or a total address count.

The exercises mainly use /23–/30, with a few /22 cross-octet cases. Ordinary LAN questions use the traditional network-and-broadcast exclusions. Every capacity question states whether its interface demand already includes the gateway and excludes growth and extra reservations. A /31 card applies only to an RFC 3021 point-to-point link; a /32 card concerns a single-address host route. Other cards separate numerical membership from connectivity and usable range from assignment availability.

The first six cards establish prefix, mask, and counting anchors. The remaining sequence mixes boundary calculations, roles, capacity choices, and repairs, moving into third-octet boundaries and later exceptions. Related variants are separated by at least three cards that ask for other facts; the review scheduler handles long-term spacing.

This is a compact recall and error-repair companion. It excludes non-unique reverse questions such as guessing an input address from a network boundary, every prefix and reverse permutation, classful shortcuts, VLSM design projects, IPv6, and device configuration. Recalling fixed examples does not establish skill on unfamiliar calculations or a working network. Learn the method with IPv4 subnetting practice, then change the addresses and solve fresh exercises. The networking flashcard study guide gives broader study context.

All exercises use artificial private or documentation addresses. Facts were checked against RFC 4632, RFC 3021, RFC 5737, RFC 1918, and Cisco’s addressing reference. The prompts, explanations, sequence, metadata, and abstract cover were independently created with AI assistance and reviewed; no source wording, exercises, diagrams, or exam material were copied. Original elements are released under CC0 1.0 to the extent applicable rights exist. This general topic deck claims no certification alignment or endorsement.

Cards in this deck

  1. Card 1

    Question

    In IPv4 CIDR notation, what does the /27 specify?

    Answer

    The first 27 bits are the network prefix. The remaining 32 − 27 = 5 bits identify positions within that address block.

  2. Card 2

    Question

    Which dotted-decimal IPv4 subnet mask matches /27?

    Answer

    255.255.255.224. The final octet is 11100000 in binary: three prefix bits after the first 24.

  3. Card 3

    Question

    How many total IPv4 addresses are in a /29 block, before excluding any addresses?

    Answer

    8 addresses. There are 32 − 29 = 3 host bits, so the block has 2^3 = 8 positions.

  4. Card 4

    Question

    To find an IPv4 network address from an address and prefix, what values must the host bits have?

    Answer

    All host bits must be zero. Keep the prefix bits unchanged; clearing the remaining bits gives the block’s first address.

  5. Card 5

    Question

    For an ordinary IPv4 LAN with a /24–/30 prefix, which two addresses are excluded from the traditional usable host count?

    Answer

    The network address and the subnet broadcast address. Traditional usable capacity is 2^(32 − prefix length) − 2; this rule is not the RFC 3021 /31 point-to-point rule.

  6. Card 6

    Question

    Which dotted-decimal IPv4 subnet mask matches /23?

    Answer

    255.255.254.0. Seven prefix bits in the third octet give 11111110; the fourth octet contains only host bits.

  7. Card 7

    Question

    What is the network address of 198.51.100.77/27?

    Answer

    198.51.100.64. The block has 32 addresses; 77 lies between the boundaries 64 and 96.

  8. Card 8

    Question

    What is the subnet broadcast address for an ordinary IPv4 LAN containing 203.0.113.149/28?

    Answer

    203.0.113.159. This block starts at .144; the next starts at .160, so the broadcast is one address before .160.

  9. Card 9

    Question

    What is the first traditionally usable host address in the ordinary IPv4 LAN containing 192.0.2.174/26?

    Answer

    192.0.2.129. The network address is .128; the first host is the next address.

  10. Card 10

    Question

    An ordinary IPv4 LAN needs 6 interface addresses in total, including its gateway. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

    Answer

    /29. Its 8 total addresses leave 6 traditional host addresses. A /30 leaves only 2.

  11. Card 11

    Question

    On an ordinary IPv4 LAN, is 198.51.100.127/27 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Subnet broadcast address. The block runs from .96 through .127; .127 has every host bit set to one.

  12. Card 12

    Question

    A learner says an ordinary IPv4 /25 LAN has 128 traditionally usable host addresses. What is the corrected usable count?

    Answer

    126 host addresses. The block has 128 total addresses; exclude its network and broadcast addresses: 128 − 2 = 126.

  13. Card 13

    Question

    What is the network address of 10.46.19.203/23?

    Answer

    10.46.18.0. Third-octet blocks start at even values; this block covers third octets 18 and 19.

  14. Card 14

    Question

    An ordinary IPv4 LAN needs 14 interface addresses total, gateway included. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

    Answer

    /28. Its 16 total addresses leave 14 traditional host addresses; a /29 leaves 6.

  15. Card 15

    Question

    What is the last traditionally usable host address in the ordinary IPv4 LAN containing 192.0.2.219/29?

    Answer

    192.0.2.222. The block is .216–.223; .223 is broadcast, so .222 is the last host.

  16. Card 16

    Question

    Do 203.0.113.126/26 and 203.0.113.129/26 belong to the same numerical IPv4 subnet?

    Answer

    No. Their network addresses are 203.0.113.64 and 203.0.113.128. A shared first three octets does not settle a /26 comparison.

  17. Card 17

    Question

    A learner gives 198.51.100.192 as the broadcast for an ordinary IPv4 LAN containing 198.51.100.173/27. What is the corrected broadcast?

    Answer

    198.51.100.191. This block starts at .160; .192 starts the next block. Broadcast is the address immediately before that next boundary.

  18. Card 18

    Question

    What is the subnet broadcast address for an ordinary IPv4 LAN containing 172.22.35.9/23?

    Answer

    172.22.35.255. The block starts at 172.22.34.0 and ends just before 172.22.36.0.

  19. Card 19

    Question

    Which IPv4 CIDR prefix length matches the subnet mask 255.255.255.240?

    Answer

    /28. The first three octets contribute 24 one bits; 240 is 11110000, contributing four more.

  20. Card 20

    Question

    An ordinary IPv4 LAN needs 15 interface addresses in total, gateway included. Exclude growth and extra reservations. Which prefix gives the smallest address block that fits?

    Answer

    /27. It leaves 30 traditional host addresses. A /28 leaves 14, which is one short.

  21. Card 21

    Question

    On an ordinary IPv4 LAN, is 10.61.13.0/23 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Traditionally usable host address. This block is 10.61.12.0–10.61.13.255; .13.0 is inside it. A final .0 does not by itself identify the network address.

  22. Card 22

    Question

    A learner gives 172.24.71.255 as the last usable host in an ordinary LAN containing 172.24.70.18/23. What is the corrected last host address?

    Answer

    172.24.71.254. The block’s broadcast is 172.24.71.255; the last traditional host address is one before it.

  23. Card 23

    Question

    What is the network address of 192.168.47.201/22?

    Answer

    192.168.44.0. Third-octet boundaries are multiples of 4; 47 falls in the block covering 44–47.

  24. Card 24

    Question

    On an ordinary IPv4 LAN, is 203.0.113.184/29 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Network address. /29 boundaries advance by 8 in the fourth octet, and 184 is a multiple of 8. This block ends at .191.

  25. Card 25

    Question

    An ordinary IPv4 LAN needs addresses for 30 endpoint interfaces plus 1 gateway interface. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

    Answer

    /26. The demand is 30 + 1 = 31; /27 leaves only 30 traditional host addresses, while /26 leaves 62.

  26. Card 26

    Question

    What is the first traditionally usable host address in the ordinary IPv4 LAN containing 10.84.51.230/23?

    Answer

    10.84.50.1. The network is 10.84.50.0; this block spans third octets 50 and 51.

  27. Card 27

    Question

    A learner treats /22 as fourth-octet blocks and reports 10.73.31.0 as the network for 10.73.31.88/22. What is the corrected network address?

    Answer

    10.73.28.0. The mask is 255.255.252.0, so boundaries advance by 4 in the third octet; this block covers 28–31.

  28. Card 28

    Question

    An IPv4 CIDR block contains exactly 128 total addresses, before exclusions. What is its prefix length?

    Answer

    /25. Since 128 = 2^7, there are 7 host bits; 32 − 7 = 25 prefix bits.

  29. Card 29

    Question

    What is the subnet broadcast address for an ordinary IPv4 LAN containing 192.0.2.46/30?

    Answer

    192.0.2.47. The 4-address block starts at .44; the next starts at .48.

  30. Card 30

    Question

    An ordinary IPv4 LAN needs 62 interface addresses in total, including the gateway. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

    Answer

    /26. Its 64 total addresses leave 62 traditional host addresses; /27 leaves 30.

  31. Card 31

    Question

    Do 10.95.24.250/23 and 10.95.25.7/23 belong to the same numerical IPv4 subnet?

    Answer

    Yes. Both have network address 10.95.24.0; a /23 here covers third octets 24 and 25.

  32. Card 32

    Question

    What is the last traditionally usable host address in the ordinary IPv4 LAN containing 172.26.86.9/22?

    Answer

    172.26.87.254. The block runs from 172.26.84.0 through broadcast 172.26.87.255.

  33. Card 33

    Question

    A learner subtracts network, broadcast, and a separate gateway reservation from a /30 LAN and reports 1 usable interface address. What is the traditional usable capacity, counting a gateway as an interface?

    Answer

    2 interface addresses. The block has 4 total addresses. Exclude network and broadcast once; a gateway, if present, occupies one of the remaining two.

  34. Card 34

    Question

    On an ordinary IPv4 LAN, is 192.168.100.255/23 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Traditionally usable host address. The block is 192.168.100.0–192.168.101.255; its broadcast is .101.255. A final .255 alone does not identify broadcast.

  35. Card 35

    Question

    An ordinary IPv4 LAN needs 63 interface addresses in total, gateway included. Exclude growth and extra reservations. Which prefix gives the smallest address block that fits?

    Answer

    /25. It leaves 126 traditional host addresses. A /26 leaves 62, so it is one short.

  36. Card 36

    Question

    What is the network address of 203.0.113.233/25?

    Answer

    203.0.113.128. The two fourth-octet blocks start at 0 and 128; 233 is in the second.

  37. Card 37

    Question

    A learner rounds 198.51.100.107/28 up to network address 198.51.100.112. What is the corrected network address?

    Answer

    198.51.100.96. Network boundaries advance by 16; 107 is inside .96–.111. Choose the containing block, not the next boundary.

  38. Card 38

    Question

    On an IPv4 point-to-point link using RFC 3021, how many endpoint addresses does 10.106.8.40/31 provide?

    Answer

    2 endpoint addresses. They are 10.106.8.40 and 10.106.8.41. In this point-to-point context, both are endpoint addresses; do not subtract network and directed broadcast.

  39. Card 39

    Question

    An IPv4 address lies in a subnet’s traditional usable host range. Does that alone prove it is free to assign?

    Answer

    No. It may already be assigned or reserved by local policy. Arithmetic gives a candidate range; address management determines availability.

  40. Card 40

    Question

    An ordinary IPv4 LAN needs 254 interface addresses in total, including the gateway. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

    Answer

    /24. It has 256 total addresses and 254 traditional host addresses; /25 leaves 126.

  41. Card 41

    Question

    What is the subnet broadcast address for an ordinary IPv4 LAN containing 10.117.58.177/22?

    Answer

    10.117.59.255. The block starts at 10.117.56.0, covers third octets 56–59, and ends just before 10.117.60.0.

  42. Card 42

    Question

    An ordinary IPv4 /27 LAN has a requirement of 30 interface addresses total, already including its gateway. A learner increases the requirement to 31. What is the corrected required interface count?

    Answer

    30 interface addresses. The gateway was already included. Count it once; the stated demand fits the /27 block’s 30 traditional host addresses.

  43. Card 43

    Question

    What destination address does the IPv4 host route 10.128.9.17/32 match?

    Answer

    10.128.9.17 only. All 32 bits are specified, so the route matches one address. It is not an ordinary multi-host LAN block.

  44. Card 44

    Question

    An ordinary IPv4 LAN needs addresses for 254 endpoint interfaces plus 1 gateway interface. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

    Answer

    /23. The demand is 255; /24 leaves only 254 traditional host addresses. /23 leaves 510.

  45. Card 45

    Question

    On an ordinary IPv4 LAN, is 172.28.92.0/22 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Network address. The third octet 92 is a multiple of 4 and all host bits are zero. The block covers third octets 92–95.

  46. Card 46

    Question

    What is the first traditionally usable host address in the ordinary IPv4 LAN containing 198.51.100.154/30?

    Answer

    198.51.100.153. The block starts at .152; its traditional hosts are .153 and .154, with broadcast .155.

  47. Card 47

    Question

    Two IPv4 interfaces have addresses in the same numerical subnet. Does that alone prove that they can communicate?

    Answer

    No. Matching subnet arithmetic does not establish a working link, compatible configuration, or permitted traffic. Those require checks on the actual network.

  48. Card 48

    Question

    On an ordinary IPv4 LAN, is 192.0.2.193/26 a network address, subnet broadcast address, or traditionally usable host address?

    Answer

    Traditionally usable host address. The block starts at .192 and broadcasts at .255; .193 is its first traditional host address.

Teal, blue, and amber trays in a horizontal row group glowing network nodes, joined by short paths.

48 cards

IPv4 Subnetting Practice Flashcards: Boundaries & Host Ranges

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