# Subnetting Speed Practice #3: Answers

This post makes no sense without reading this post first. The earlier post lists 5 subnetting problems, and tells you to time yourself. The answers are below the fold in this post. Don’t look til you try it for yourself! Post questions if you have them.

1) 9.200.200.200/15

2) 100.100.100.100/19

3) 151.151.151.151/23

4) 201.201.201.201/27

5) 223.223.221.221/30

 Problem Network Bits Subnet Bits Host Bits # Hosts 1 8 7 17 131,070 2 8 11 13 8190 3 16 7 9 510 4 24 3 5 30 5 24 6 2 2

The following table lists the subnet ID and subnet broadcast address. It does not list the range of addresses; the range of usable addresses is simply the range of numbers between the subnet ID and subnet broadcast address.

 Problem Subnet ID Broadcast Address 1 9.200.0.0 9.201.255.255 2 100.100.96.0 100.100.127.255 3 151.151.150.0 151.151.151.255 4 201.201.201.192 201.201.201.223 5 223.223.221.220 223.223.221.223
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Gavin
May 8, 2017 9:50 am

6 minutes for all 5. On average I find it takes me about a minutes if there’s an “interesting” octet. 45s otherwise. Thanks for posting these practice drills and questions – they are helpful in prepping for the CCENT.

lyjo
May 9, 2017 9:41 am

You’re welcome, Gavin! Keep up the practice – even a 25% reduction in time required is a big help on exam day.

Maxim
February 13, 2018 7:18 am

There is a mistake in the answer on Problem 2’s Network bit and Subnet bit – it’s class B network.

Maxim