Networking Concepts
Subnetworks
Figure
Now, refer again to example 1. The subnet mask must indicate that three bits of the node portion of the IP address will be used for the subnet identifier. The subnet mask turns on (sets to 1) all the relevant bits for its subnet scheme. The subnet mask for example 1 is shown below. Note that the most significant three bits of the rightmost byte are set.
Subnet Mask
Binary 11111111.11111111.11111111 11100000
Decimal 255.255.255 224
Table
Column 2 shows the values, in binary, of the six subnet addresses. Five zeroes are shown in parentheses to indicate where the three
The table shows that subnets of 30 nodes each are possible given a subnet mask of 255.255.255 224. This is derived from the column that shows the range of possible values for the five bits that make up the node portion of the IP address. The range for each of the six subnets shows 30 possible values.
Chapter 2 | 29 |