ZyAIR
Divide the network 192.168.1.0 into two separate subnets by converting one of the host ID bits of the IP address to a network number bit. The “borrowed” host ID bit can be either “0” or “1” thus giving two subnets; 192.168.1.0 with mask 255.255.255.128 and 192.168.1.128 with mask 255.255.255.128.
In the following charts, shaded/bolded last octet bit values indicate host ID bits “borrowed” to form network ID bits. The number of “borrowed” host ID bits determines the number of subnets you can have. The remaining number of host ID bits (after “borrowing”) determines the number of hosts you can have on each subnet.
Chart
| NETWORK NUMBER |
| LAST OCTET BIT VALUE | ||
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IP Address | 192.168.1. |
| 0 | ||
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IP Address (Binary) | 11000000.10101000.00000001. |
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| 0000000 | |
0 | |||||
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Subnet Mask | 255.255.255. |
| 128 | ||
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Subnet Mask (Binary) | 11111111.11111111.11111111. |
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| 0000000 | |
1 | |||||
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Subnet Address: 192.168.1.0 |
| Lowest Host ID: 192.168.1.1 | |||
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Broadcast Address: 192.168.1.127 | Highest Host ID: 192.168.1.126 | ||||
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| Chart |
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| NETWORK NUMBER |
| LAST OCTET BIT VALUE | ||
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IP Address | 192.168.1. |
| 128 | ||
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IP Address (Binary) | 11000000.10101000.00000001. |
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| 0000000 | |
1 | |||||
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Subnet Mask | 255.255.255. |
| 128 | ||
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Subnet Mask (Binary) | 11111111.11111111.11111111. |
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| 0000000 | |
1 | |||||
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Subnet Address: 192.168.1.128 | Lowest Host ID: 192.168.1.129 | ||||
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Broadcast Address: 192.168.1.255 | Highest Host ID: 192.168.1.254 | ||||
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The remaining 7 bits determine the number of hosts each subnet can have. Host IDs of all zeros represent the subnet itself and host IDs of all ones are the broadcast address for that subnet, so the actual number of hosts available on each subnet in the example above is 27 – 2 or 126 hosts for each subnet.
192.168.1.0 with mask 255.255.255.128 is the subnet itself, and 192.168.1.127 with mask 255.255.255.128 is the directed broadcast address for the first subnet. Therefore, the lowest IP address that can be assigned
IP Subnetting |