VLSM allows network engineers to divide an IP address space into a hierarchy of subnets of different sizes, making it possible to create subnets with very different host counts without wasting large numbers of addresses. Source: https://goo.gl/6zkkn1

1. VLSM
Variable Length Subnet Mask

2. VLSM
Department Required
IP addresses
CSE 4000
EEE 1000
ME 900
CHEM 800
MATH 500
LINK1 2
LINK2 2
LINK3 2
Given IP Block: 172.12.0.0/16

3. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002
EEE-1002
ME-902
CHEM-802
MATH-502
LINK1-4
LINK2-4
LINK3-4

4. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002
ME-902
CHEM-802
MATH-502
LINK1-4
LINK2-4
LINK3-4
For CSE Detp. ----- 211=2048 (Requirement not fulfilled)
212=4076 (Requirement fulfilled)
Calculating Host bit

5. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902
CHEM-802
MATH-502
LINK1-4
LINK2-4
LINK3-4
For EEE Detp. ----- 29=512 (Requirement not fulfilled)
210=1024 (Requirement fulfilled)
Calculating Host bit

6. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802
MATH-502
LINK1-4
LINK2-4
LINK3-4
For ME Detp. ----- 29=512 (Requirement not fulfilled)
210=1024 (Requirement fulfilled)
Calculating Host bit

7. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502
LINK1-4
LINK2-4
LINK3-4
Calculating Host bit
For CHEM Detp. ----- 29=512 (Requirement not fulfilled)
210=1024 (Requirement fulfilled)

8. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4
LINK2-4
LINK3-4
For MATH Detp. ----- 28=256 (Requirement not fulfilled)
29=512 (Requirement fulfilled)
Calculating Host bit

9. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4
LINK3-4
For LINK1 ----- 21=2 (Requirement not fulfilled)
22=4 (Requirement fulfilled)
Calculating Host bit

10. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4
Calculating Host bit
For LINK2 ----- 21=2 (Requirement not fulfilled)
22=4 (Requirement fulfilled)

11. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Host bit
For LINK3 ----- 21=2 (Requirement not fulfilled)
22=4 (Requirement fulfilled)

12. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
First network address will be the given network address block (172.12.0.0)
Calculating Network Address

13. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
First network address will be the given network address block (172.12.0.0)
Calculating Network Address

14. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095

15. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095

16. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839

17. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583

18. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327

19. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071

20. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815

21. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559

22. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303

23. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047

24. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791

25. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535

26. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535
4095 − 256*11 = 1279

27. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535
4095 − 256*11 = 1279
4095 − 256*12 = 1023

28. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535
4095 − 256*11 = 1279
4095 − 256*12 = 1023
4095 − 256*13 = 767

29. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535
4095 − 256*11 = 1279
4095 − 256*12 = 1023
4095 − 256*13 = 767
4095 − 256*14 = 511

30. VLSM
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*1 = 3839
4095 − 256*2 = 3583
4095 − 256*3 = 3327
4095 − 256*4 = 3071
4095 − 256*5 = 2815
4095 − 256*6 = 2559
4095 − 256*7 = 2303
4095 − 256*8 = 2047
4095 − 256*9 = 1791
4095 − 256*10 = 1535
4095 − 256*11 = 1279
4095 − 256*12 = 1023
4095 − 256*13 = 767
4095 − 256*14 = 511
4095 − 256*15 = 255

31. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*15 = 255

32. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Broadcast Address
For CSE Detp. 212 −1 =4095
4095 − 256*15 = 255

33. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network Address
The Network Address of EEE Dept. will be “Previous Broadcast Address + 1”
Therefore 172.12.15.255 + 1 = 172.12.16.0

34. VLSM
How Octet Changes
9:00:59 AM
9:00:59+1 AM
9:01:00 AM
172.12.0.255
192.168.0.255+1
172.12.1.0

35. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network Address
The Network Address of EEE Dept. will be “Previous Broadcast Address + 1”
Therefore 172.12.15.255 + 1 = 172.12.16.0
And so son……

36. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network Address
The Network Address of EEE Dept. will be “Previous Broadcast Address + 1”
Therefore 172.12.15.255 + 1 = 172.16.0
And so son……

37. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network & Broadcast Address

38. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network & Broadcast Address

39. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2
LINK2-4 2
LINK3-4 2
Calculating Next Network & Broadcast Address

40. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2
LINK3-4 2
Calculating Next Network & Broadcast Address

41. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2
Calculating Next Network & Broadcast Address

42. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating Next Network & Broadcast Address

43. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1
Ex: The First Usable IP of CSE Dept. is 172.12.0.0 + 1 = 172.12.0.1

44. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1
Ex: The First Usable IP of CSE Dept. is 172.12.0.0 + 1 = 172.12.0.1

45. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

46. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

47. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

48. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

49. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

50. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

51. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

52. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The First Usable IP will be “Network Address + 1

53. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1
Ex: The Last Usable IP of CSE Dept. is 172.15.12.255

54. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1
Ex: The Last Usable IP of CSE Dept. is 172.15.12.255

55. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

56. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

57. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

58. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

59. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

60. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

61. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating First Usable IP
The Last Usable IP will be “Broadcast Address - 1

62. VLSM
Calculating Subnetmask
IP Address 32 bits
Host bits of CSE Dept. = 12
The network bit of CSE Dept. = 32 – 12 = 20 bits
11111111.11111111.11110000.00000000
255 . 255 . 240 . 0
Subnet
Value
Bit Value
128 64 32 16 8 4 2 1
255 1 1 1 1 1 1 1 1
254 1 1 1 1 1 1 1 0
252 1 1 1 1 1 1 0 0
248 1 1 1 1 1 0 0 0
240 1 1 1 1 0 0 0 0
224 1 1 1 0 0 0 0 0
192 1 1 0 0 0 0 0 0
128 1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0

63. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

64. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

65. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

66. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254 255.255.252.0
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

67. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254 255.255.252.0
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254 255.255.254.0
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

68. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254 255.255.252.0
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254 255.255.254.0
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2 255.255.255.252
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

69. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254 255.255.252.0
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254 255.255.254.0
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2 255.255.255.252
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6 255.255.255.252
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10
Calculating Subnet Mask

70. VLSM
Department
&
Required IP
Host
bit
(n)
Network
Address
Broadcast
Address
First
Usable IP
Last
Usable IP
Subnet Mask
CSE-4002 12 172.12.0.0 172.12.15.255 172.12.0.1 172.12.15.254 255.255.240.0
EEE-1002 10 172.12.16.0 172.12.19.255 172.12.16.1 172.12.19.254 255.255.252.0
ME-902 10 172.12.20.0 172.12.23.255 172.12.20.1 172.12.23.254 255.255.252.0
CHEM-802 10 172.12.24.0 172.12.27.255 172.12.24.1 172.12.27.254 255.255.252.0
MATH-502 9 172.12.28.0 172.12.29.255 172.12.28.1 172.12.29.254 255.255.254.0
LINK1-4 2 172.12.30.0 172.12.30.3 172.12.30.1 172.12.30.2 255.255.255.252
LINK2-4 2 172.12.30.4 172.12.30.7 172.12.30.5 172.12.30.6 255.255.255.252
LINK3-4 2 172.12.30.8 172.12.30.11 172.12.30.9 172.12.30.10 255.255.255.252
Calculating Subnet Mask

71. Thank You
 Prepared by
 Md. Jamal Hossain
 Dept. of Computer Science & Engineering (SUB)
 CCNA Routing & Switching (BUET)
 Redhat Certified System Administrator (CSL)
 facebook: www.facebook.com/jh1337.cse
 YouTube: www.youtube.com/jamalhossain1337
 Email: jamalhossain.cse@gmail.com
All rights are reserved