**Contents**show

## How many hosts can be addressed on a subnet that has 7 host bits?

Subnetting a Class C network address

Mask | Binary | # Host bits |
---|---|---|

255.255.255.128 | 10000000 |
7 |

255.255.255.192 | 11000000 | 6 |

255.255.255.224 | 11100000 | 5 |

255.255.255.240 | 11110000 | 4 |

## How many subnets can be created by borrowing these bits?

Broadcast address:

1.0 network but now we want to have **4 subnets**. For every host-bit we borrow we can double the number of subnets we can create, so by borrowing 2 host bits we can create 4 subnets. Every host bit you “borrow” doubles the amount of subnets you can create.

## How do you calculate the number of subnets in a bit?

Calculate the subnet bits by **looking at the final 8-bit binary word of the 32-bit binary subnet mask**. If the final 8-bit binary word is 10000000, then there is one subnet bit and therefore 25 mask bits. If it is 11000000, then there are two subnet bits and therefore 26 mask bits.

## How many bits do you need to borrow from the subnet field to borrow 3 bits 1 bit would give us 2 subnets 2 give us 4 and 3 would give us 8?

1.0/24 network. You need to create 8 subnets. How many bits do you need to borrow from the host field for the subnet field? We need to borrow 3 bits: 1 bit would give us 2 subnets, 2 would give us **4**, and 3 would give us 8.

## How many hosts are in a 8 subnet?

Subnet Cheat Sheet – 24 Subnet Mask, 30, 26, 27, 29, and other IP Address CIDR Network References

CIDR | Subnet mask | # of IP addresses |
---|---|---|

/10 | 255.192.0.0 | 4,194,304 |

/9 | 255.128.0.0 | 8,388,608 |

/8 | 255.0.0.0 | 16,777,216 |

/7 | 254.0.0.0 | 33,554,432 |

## How many hosts are in a 25 subnet?

Subnet Mask Cheat Sheet

Addresses | Hosts | |
---|---|---|

/ 25 | 128 |
126 |

/ 24 | 256 | 254 |

/ 23 | 512 | 510 |

/ 22 | 1024 | 1022 |

## How many subnets can you create if you borrow 10 bits of a class B network?

(1) A **1,000 subnets** are needed: 210 = 1024, therefore ten bits must be borrowed. (2) When borrowing ten bits in a class B address, the binary subnet mask, is 11111111.11111111. 11111111.11000000.