So the question remains, when is this useful?ģ:24 – This subnet mask is used when an exact match to an IP Address is required. When a subnet mask that is all 1s is used, the network prefix will always be the same as the original IP address. It is no surprise in this case, that the host identifier will be 0.0.0.0 this is because no bits have been assigned to the host part. The will allow the network prefix and host identifier to be found. So what happens when you are given an IP address like this one where all the subnet mask bits are set to one? First the IP Address and the subnet mask are applied. To understand more about subnets, let’s have a look at why this is the case.Ģ:37 – The subnet mask divides an IP Address into a network and host identifier. Notice also, that in the top two subnets, there are no subnets or hosts available. As the number of 1 bits in the subnet mask decreases, more hosts are available per subnet, however fewer subnets are available. Notice too, that the number of subnets and hosts that are available depending on which subnet mask is used.
Since 1s and 0s must be contiguous, certain decimals will always be used. Due to this, notice in very first column, the last decimal in the IP address. First, you can see subnet masks always have 1s on the left hand side while there are zeros on the right hand side. If you do not feel confident in your decimal and binary skills, I would suggest looking at our previous video of converting decimals as it goes into this process in more detail.ġ:47 – Shown here are some examples of subnet masks. If you understand this process, then you are all set to start looking into subnetting. This will give the decimal number in binary. The process is repeated until all the values are calculated. The new value, 58, is compared to the powers of 2 value. Since the value was higher, the powers of 2 value which is 128 is subtracted from the value. If it is higher, which it is, a 1 is recorded. This time the value that is to be converted, 186 is compared with the powers of 2. To convert it to binary, the powers of 2 are used again. Now let’s have a look at converting decimal to binary.Ġ:57 – Let’s consider the same value. Once all the totals have been worked out, it just a matter of adding them up to get the value. If the value is a 1, the power of 2 value is used, otherwise the total is a zero. Using this value will give us the last row of the table. To convert the binary number, it is just a matter of adding it to the table. Each binary position has a value based on a power of 2. If I want to convert the following binary number to decimal I would use the following table. This is an important skill to know when subnetting so I will do a quick review.
#Quick ipv4 subnet mask table how to
0:10 – In a previous video, I looked at how to convert from decimal to binary and binary to decimal.
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