### Discussion :: Subnetting - Subnetting (Q.No.4)

Nikhil said: (Feb 8, 2014) | |

255.255.255.224 i.e Binary of 255 is 11111111 and Binary number of 224 is 11100000. Here 1 Represent On bit and 0 represents Off bit. Then how to calculate Host Id. See Here, Formula Host Id = 2^off bit - 2 i.e 2^5 = 32 - 2 = 30. And Net Id is = 2^on bit = 2^3 = 8. That's why Answer is 30. |

Rahul said: (Mar 11, 2015) | |

Simple. = 256-224 = 32. And here first add is network add and last one is broadcast so we are supposed to subtract these two add from 32. So max host we will connect = 30. |

Pratik said: (Jul 8, 2015) | |

Thanks @Nikhil but can you explain that binary conversions till 255? |

Narsing said: (Jun 16, 2016) | |

Decimal to binary conversion: 255.255.255.255 128 64 32 16 8 4 2 1 2 to the power of 7 = 128. 2 to the power of 6 = 64 . 1 1 1 1 1 1 1 1 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255. 11111111.11111111.11111111.11111111 255 255 255 255 Eg: 192.168.10.10 192-- 128 64 32 16 8 4 2 1 ------> 1 1 0 0 0 0 0 0 168 --> 1 0 1 0 1 0 0 0 10 ---> 0 0 0 0 1 0 1 0 10 ---> 0 0 0 0 1 0 1 0 That means where is the 1 is there will add those numbes, so will get decimal number. |

Sagar said: (Nov 29, 2016) | |

Your answer is easy to understand, Thanks @Nikhil. |

Vasundhra said: (Jan 4, 2017) | |

Not able to perceive, please explain in an easy way. Is there any formula to calculate subnet mask? |

Darth Vader said: (Apr 3, 2017) | |

Convert it to binary: 11111111.11111111.11111111.11100000. You can't use 1s because they are mask bits, you can use 0s as host bits and they can get values between 0 to 31 (total 32 values). 2 of these 32 host values cannot be used as a host IP because one of them belong to broadcast and the other belong to the network address. There is a formula for this host calculation it is 2^(host bits)-2 For this example it is 2^5 - 2 = 32-2 = 30. |

Chaithanya said: (Jun 13, 2017) | |

24|27 = 3bits on 5 bits off. 2^h-2 h=hostsbits = 5, 32-2 = 30. Or simple total is 256 so 256-224=30. |

Dhananjay said: (Aug 25, 2017) | |

Thanks. |

Seonti said: (Sep 3, 2017) | |

Can anyone explain why it is /27? |

Nishu Kumar said: (Sep 24, 2017) | |

(1)255.255.255.224 128+64+32=224. 2^3 =8, 2^5-2= 32 -2 =30 (2) formula; Block size = 256 - Actual subnet mask, =256 -224, = 32. |

Tara said: (Dec 9, 2017) | |

@Seonti. Here the question is 255.255.255.224. Convert to binary it is 11111111 11111111 11111111 11100000. Count nos of 1 ...it is 27. |

Bijay Kc said: (Apr 5, 2018) | |

Thank you @Nikhil. |

Ankit Chaturvedi said: (Apr 30, 2018) | |

Total host= 2^( use off bits) - 2. |

Nikita said: (Aug 2, 2019) | |

Thank you all for explaining it. |

Melin said: (Apr 30, 2020) | |

Thanks for the explanation. |

Neha said: (Nov 24, 2020) | |

Thanks all. |

Jayden said: (Sep 24, 2021) | |

255.255.255.224 convert to binary: 11111111.11111111.11111111.11100000 = /27 bits, 5 bits left for hosts, subnet-mask has 32, therefore 32 - 27 = 5, 2^5 - 2 = 32 - 2 = 30. |

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