Class B Example
In Figure 4-23, we will determine the addressing for a Class B network with a nondefault
mask. Given the address of 172.16.139.46 and knowing that the subnet mask is
255.255.240.0, or /20, you can determine the subnet and host addresses for this network.
Figure 4-23 Class B Address with Nondefault Subnet Mask
Table 4-3 Subnet Addresses Table
Subnet No. Subnet ID Host Range Broadcast Address
1 192.168.5.32 192.168.5.33 to 192.168.5.62 192.168.5.63
2 192.168.5.64 192.168.5.65 to 192.168.5.94 192.168.5.95
3 192.168.5.96 192.168.5.97 to 192.168.5.126 192.168.5.127
4 192.168.5.128 192.168.5.129 to 192.168.5.158 192.168.5.159
5 192.168.5.160 192.168.5.161 to 192.168.5.190 192.168.5.191
6 192.168.5.192 192.168.5.193 to 192.168.5.222 192.168.5.223
IP Address 172.16.139.46 Subnet Mask /20
IP Address 172
10101100
172
172
172
172
172
10101100
11111111
16
00010000
16
16
16
16
16
00010000
11111111
139
10000000
10000000
128
1000 1011
1111 0000
46
00000000
0
00101110
00000000
00000001=128.1
11111110=143.254
11111111=143.255
00000000=144.0
/20
IP Address
Subnet Mask
Subnetwork
Subnetwork
First Host
Last Host
Directed
Broadcast
Next Subnet
10000000
10001111
10001111
10010000
268 Chapter 4: LAN Connections
The following outlines the steps and shows the details of each operation in the eight-step
process:
Step 1 Write the octet that is being split in binary (10001011).
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