IP Cheat Sheet



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IP Cheat Sheet

Published on 11/23/2004 This Article gives some basic IP info at a glance including how to count in binary and figure out hosts and subnets.

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IP Cheat Sheet

 So you find binary complicated.  Join the club.  This cheat sheet was designed to help one get a quick reference and understanding of how to calculate subnets and hosts on a network. It is a basic sheet for those who have a general concept of calculating TCP/IP networks and hosts but need a little assistance here and there.

Cheat Sheet

  __    __    __   __   __   __   __   __

  27      26     25     24    23     22     21    20

128     64    32     16     8       4      2      1

____.____.____.____(Each refers to an Octet)

 1st      2nd    3rd     4th

| |1st Octet |Default Mask |# Networks |# Hosts |

| |Start | | | |

|Class A |0 |255.0.0.0 |1 |16,777,244 |

|Class B |10 |255.255.0.0 |1 |65,534 |

|Class C |110 |255.255.255.0 |1 |254 |

Class A

|Number of |Number of Hosts|Required # of |Subnet Mask |

|Subnets |per Subnet |bits | |

|0 |Invalid |1 |Invalid |

|2 |4,194,302 |2 |255.192.0.0 |

|6 |2,097,150 |3 |255.224.0.0 |

|14 |1,048,574 |4 |255.240.0.0 |

|30 |524,286 |5 |255.248.0.0 |

|62 |262,142 |6 |255.252.0.0 |

|126 |131,070 |7 |255.254.0.0 |

|254 |65,534 |8 |255.255.0.0 |

Class B

|Number of |Number of Hosts|Required # of |Subnet Mask |

|Subnets |per Subnet |bits | |

|0 |Invalid |1 |Invalid |

|2 |16,382 |2 |255.255.192.0 |

|6 |8,190 |3 |255.255.224.0 |

|14 |4,094 |4 |255.255.240.0 |

|30 |2,046 |5 |255.255.248.0 |

|62 |1,022 |6 |255.255.252.0 |

|126 |510 |7 |255.255.254.0 |

|254 |254 |8 |255.255.255.0 |

Class C

|Number of |Number of Hosts|Required # of |Subnet Mask |

|Subnets |per subnet |bits | |

|0 |Invalid |1 |Invalid |

|2 |62 |2 |255.255.255.192 |

|6 |30 |3 |255.255.255.224 |

|14 |14 |4 |255.255.255.240 |

|30 |6 |5 |255.255.255.248 |

|62 |2 |6 |255.255.255.252 |

|126 |Invalid |7 |Invalid |

|254 |Invalid |8 |Invalid |

2y - 2 = X

To find how many Networks or Hosts

with an existing subnet mask

ØTo find out how many subnets (networks)you can have out of a subnet mask, count all 1’s in thatnetwork octet.

ØTo find out how many hosts I can have on each subnet, count all the zeros after the last 1 in the network octet and the remanding octets.

2Y> = X

Planning out yourSubnets.  No existing subnet mask

To find out what subnet mask will be based on the number of Subnets you need, put in the desired number of subnets for the Xvalue. Y is the number ones you will steal from the host bits.

2Y >= X

Planning your Subnet based on Hosts

ØTo find out what your subnet mask will be based on the number of hosts you need, put in the desired number of hosts as your X value.Y is the number of zero’s you will put in from the rightmostbit in the last octet.

Counting In binary

|Decimal |Binary |

|0 |00000000 |

|1 |00000001 |

|2 |00000010 |

|3 |00000011 |

|4 |00000100 |

|5 |00000101 |

|6 |00000110 |

|7 |00000111 |

|8 |00001000 |

|9 |00001001 |

|10 |00001010 |

|11 |00001011 |

|12 |00001100 |

And so on ….

 

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