Easy Subnetting

SUBNETTING

Increasing the number of network bits and decreasing the number of host bits is called subnetting.

Class C: In class c we can subnet from 1 to 6.

One bit subnetting: 192.168.0.00000000/25 mask: 255.255.255.128

Total subnets: 2¹=2. Total host in each subnet: 2⁷-2=126.

We minus last subnet mask value from 256 to find next subnet id. Ex: 256-128=128. Or Network id+ total host= last IP.

Two bits subnetting: 192.168.0.00000000/26 mask: 255.255.255.192

Total subnets: 2²=4. Total host in each subnet: 2⁶-2=62.

Three bits subnetting: 192.168.0.00000000/27 mask: 255.255.255.224

Total subnets: 2³=8. Total host in each subnet: 2⁵-2=30.

Four bits subnetting: 192.168.0.00000000/28 mask: 255.255.255.240

Total subnets: 2⁴=16. Total host in each subnet: 2⁴-2=14.

Five bits subnetting: 192.168.0.00000000/29 mask: 255.255.255.248

Total subnets: 2⁵=32. Total host in each subnet: 2³-2=6.

Six bits subnetting: 192.168.0.00000000/30 mask: 255.255.255.252

Total subnets: 2⁶=64. Total host in each subnet: 2²-2=2.

Class B: In class b we can subnet from 1 to 14.

One bit subnetting: 172.16.00000000.0/17 mask: 255.255.128.0

Total subnets: 2¹=2. Total host in each subnet: 2¹⁵-2=32766.

Two bits subnetting: 172.16.00000000.0/18 mask: 255.255.192.0

Total subnets: 2²=4. Total host in each subnet: 2¹⁴-2=16382.

Three bits subnetting: 172.16.00000000.0/19 mask: 255.255.224.0

Total subnets: 2³=8. Total host in each subnet: 2¹³-2=8190.

Four bits subnetting: 172.16.00000000.0/20 mask: 255.255.240.0

Total subnets: 2⁴=16. Total host in each subnet: 2¹²-2=4094.

Five bits subnetting: 172.16.00000000.0/21 mask: 255.255.248.0

Total subnets: 2⁵=32. Total host in each subnet: 2¹¹-2=2046.

Six bits subnetting: 172.16.00000000.0/22 mask: 255.255.252.0

Total subnets: 2⁶=64. Total host in each subnet: 2¹⁰-2=1022.

Seven bits subnetting: 172.16.00000000.0/23 mask: 255.255.254.0

Total subnets: 2⁷=128. Total host in each subnet: 2⁹-2=510.

Eight bits subnetting: 172.16.00000000.0/24 mask: 255.255.255.0

Total subnets: 2⁸=256. Total host in each subnet: 2⁸-2=254.

Nine bits subnetting: 172.16.0.00000000/25 mask: 255.255.255.128

Total subnets: 2⁹=512. Total host in each subnet: 2⁷-2=126.

Ten bits subnetting: 172.16.0.00000000/26 mask: 255.255.255.192

Total subnets: 2¹⁰=1024. Total host in each subnet: 2⁶-2=62.

Eleven bits subnetting: 172.16.0.00000000/27 mask: 255.255.255.224

Total subnets: 2¹¹=2048. Total host in each subnet: 2⁵-2=30.

Twelve bits subnetting: 172.16.0.00000000/28 mask: 255.255.255.240

Total subnets: 2¹²=4094. Total host in each subnet: 2⁴-2=14.

Thirteen bits subnetting:172.16.0.00000000/29 mask: 255.255.255.248

Total subnets: 2¹³=8192. Total host in each subnet: 2³-2=6.

Fourteen bits subnetting:172.16.0.00000000/30 mask: 255.255.255.252

Total subnets: 2¹⁴=16384. Total host in each subnet: 2²-2=2.

Class A: In class A we can subnet from 1 to 22.

One bit subnetting: 10.00000000.0.0/9 mask: 255.128.0.0

Total subnets: 2¹=2. Total host in each subnet: 2²³-2=8388606.

Two bits subnetting: 10.00000000.0.0/10 mask: 255.192.0.0

Total subnets: 2²=4. Total host in each subnet: 2²²-2=4194302.

Three bits subnetting: 10.00000000.0.0/11 mask: 255.224.0.0

Total subnets: 2³=8. Total host in each subnet: 2²¹-2=2097150.

Four bits subnetting: 10.00000000.0.0/12 mask: 255.240.0.0

Total subnets: 2⁴=16. Total host in each subnet: 2²⁰-2=1048574.

Five bits subnetting: 10.00000000.0.0/13 mask: 255.248.0.0

Total subnets: 2⁵=32. Total host in each subnet: 2¹⁹-2=524286.

Six bits subnetting: 10.00000000.0.0/14 mask: 255.252.0.0

Total subnets: 2⁶=64. Total host in each subnet: 2¹⁸-2=262142.

Seven bits subnetting: 10.00000000.0.0/15 mask: 255.254.0.0

Total subnets: 2⁷=128. Total host in each subnet: 2¹⁷-2=131070.

Eight bits subnetting: 10.00000000.0.0/16 mask: 255.255.0.0

Total subnets: 2⁸=256. Total host in each subnet: 2¹⁶-2=65534.

Nine bits subnetting: 10.0.00000000.0/17 mask: 255.255.128.0

Total subnets: 2⁹=512. Total host in each subnet: 2¹⁵-2=32766.

Ten bits subnetting: 10.0.00000000.0/18 mask: 255.255.192.0

Total subnets: 2¹⁰=1024. Total host in each subnet: 2¹⁴-2=16382.

Eleven bits subnetting: 10.0.00000000.0/19 mask: 255.255.224.0

Total subnets: 2¹¹=2048. Total host in each subnet: 2¹³-2=8190.

Twelve bits subnetting: 10.0.00000000.0/20 mask: 255.255.240.0

Total subnets: 2¹²=4096. Total host in each subnet: 2¹²-2=4094.

Thirteen bits subnetting:10.0.00000000.0/21 mask: 255.255.248.0

Total subnets: 2¹³=8192. Total host in each subnet: 2¹¹-2=2046.

Fourteen bits subnetting:10.0.00000000.0/22 mask: 255.255.252.0

Total subnets: 2¹⁴=16384. Total host in each subnet: 2¹⁰-2=1022.

Fifteen bits subnetting:10.0.00000000.0/23 mask: 255.255.254.0

Total subnets: 2¹⁵=32768. Total host in each subnet: 2⁹-2=510.

Sixteen bits subnetting:10.0.00000000.0/24 mask: 255.255.255.0

Total subnets: 2¹⁶=65536. Total host in each subnet: 2⁸-2=254.

Seventeen bits subnetting:10.0.0.00000000/25 mask: 255.255.255.128

Total subnets: 2¹⁷=131072. Total host in each subnet: 2⁷-2=126.

Eighteen bits subnetting:10.0.0.00000000/26 mask: 255.255.255.192

Total subnets: 2¹⁸=262144. Total host in each subnet: 2⁶-2=62.

Nineteen bits subnetting:10.0.0.00000000/27 mask: 255.255.255.224

Total subnets: 2¹⁹=524288. Total host in each subnet: 2⁵-2=30.

Twenty bits subnetting: 10.0.0.00000000/28 mask: 255.255.255.240

Total subnets: 2²⁰=1048576. Total host in each subnet: 2⁴-2=14.

Twenty one bits subnetting:10.0.0.00000000/29 mask: 255.255.255.248

Total subnets: 2²¹=2097152. Total host in each subnet: 2³-2=6.

Twenty two bits subnetting:10.0.0.00000000/30 mask: 255.255.255.252

Total subnets: 2²²=4194304. Total host in each subnet: 2²-2=2.

IPV4 Addresses

IPv4 Addresses

IP addresses develop by IETF (Internet Engineering Task Force).

IP is network layer routed protocol, which are use for numeric identification of a device on TCP/IP network.

• Binary numeric system: represent data in bits 0 or 1
• Decimal numeric system: represent data in digits, 0-9
• Hexa decimal numeric system: represent data in 0-9 and A-F

Mac address is a hexa decimal format, which consist of 12 hexa (48 bits). 1 Hexa=4bits. Authorized by IEEE (Institute of Electrical Electronic Engineering).

• First 6 hexa of Mac address called OUI (Organization Unique Identifier), we can’t change it
• Second 6 hexa of Mac address called vender assign numbers

We have five classes of IP addresses: A, B, C, D, E

Class A: Range (0-127). Rule: first bit of first byte must be off, at least one bit from the remaining must be on. Ex: 01000000.

Total network and host in class A: 2^n-1, where n=number of network bits. 2^8-1 -2=2⁷-2=126 (networks).

2^P-2, where p=number of host bits. 2²⁴ -2=16777214 (hosts).

Class B: Range (128-191). Rule: first bit of first byte must be on second bit of first byte must be off, remaining bits may be on or off. Ex: 10111001.

Total network and host in class B: 2^n-2, where n=number of network bits. 2^16-2=2¹⁴ =16384  (networks).

2^P-2, where p=number of host bits. 2¹⁶-2=65534 (hosts).

Class C: Range (192-223). Rule: first bit of first byte must be on second bit of first byte must be on third bit of first byte must be off, at least the remaining bits may be on or off. Ex: 11010000.

Total network and host in class C: 2^n-3, where n=number of network bits. 2^24-3=2²¹=2097152 (networks).

2^P-2, where p=number of host bits. 2⁸-2=254 (hosts).

Class D: Range (224-239). Use for multicasting, no network and host portion.

Class E: Range (240-255). Reserved for IETF, use for research purposes. No network and no host portion.

Subnet mask: Define the network and host portion, in subnet mask on bits are called network portion and off bits are called host portion.

Ex: 192.168.1.0 255.255.255.0/24

CIDR: (Classless inter domain routing) or Prefix, /24.

Private and Public IPs

Private IPs: 192.168.0.0-192.168.255.255, 172.16.0.0-172.31.255.255, 10.0.0.0-10.255.255.255. Except these IPs all IPs are called Public IPs.

Understanding the power of 2: Power of 2 is important to understand and memorize for use with IP subnetting.

2¹=2, 2²=4, 2³=8, 2⁴=16, 2⁵=32, 2⁶=64, 2⁷=128, 2⁸=256, 2⁹=512, 2¹⁰=1024, 2¹¹=2048, 2¹²=4096, 2¹³=8192, 2¹⁴=16384 etc.