Subnetting a Class C Address into
8 x 30 address subnets

EG Class C Address of 10.5.3.0

If a single net, Netmask is 255.255.255.0 & 254 addresses are available on the net.

To subnet the Class C Address we use the most significant three bits of the least significant byte to determine the network:

Position 7 6 5 4 3 2 1 0
Decimal 128 64 32 16 8 4 2 1
Netmask 1 1 1 x x x x x

So the last byte of the netmask becomes 128 + 64 + 32 = 224.

The addresses available on net 0 are:

Position 7 6 5 4 3 2 1 0
Decimal 128 64 32 16 8 4 2 1
Netmask x x x 1 1 1 1 1

IE 0 to 16 + 8 + 4 + 2 + 1 = 31 makes 32 addresses.

But binary xxx00000 (0) is the network address and xxx11111 (31) is the broadcast address leaving 1 to 30 available for stations.

The complete set of subnets is:

Net Net Address Broadcast Address Available Addresses CDIR Notation
0 10.5.3.0 10.5.3.31 10.5.3.1 - 10.5.3.30 10.5.3.0/255.255.255.224
1 10.5.3.32 10.5.3.63 10.5.3.33 - 10.5.3.62 10.5.3.32/255.255.255.224
2 10.5.3.64 10.5.3.95 10.5.3.65 - 10.5.3.94 10.5.3.64/255.255.255.224
3 10.5.3.96 10.5.3.127 10.5.3.97 - 10.5.3.126 10.5.3.96/255.255.255.224
4 10.5.3.128 10.5.3.159 10.5.3.129 - 10.5.3.158 10.5.3.128/255.255.255.224
5 10.5.3.160 10.5.3.191 10.5.3.161 - 10.5.3.190 10.5.3.160/255.255.255.224
6 10.5.3.192 10.5.3.223 10.5.3.193 - 10.5.3.222 10.5.3.192/255.255.255.224
7 10.5.3.224 10.5.3.255 10.5.3.225 - 10.5.3.254 10.5.3.224/255.255.255.224

Subnets for 8 Station Blocks:

Net Net Address Broadcast Address Available Addresses CDIR Notation
1 10.5.3.0 10.5.3.7 10.5.3.1 - 10.5.3.6 10.5.3.0/255.255.255.248
2 10.5.3.8 10.5.3.15 10.5.3.9 - 10.5.3.14 10.5.3.8/255.255.255.248
3 10.5.3.16 10.5.3.23 10.5.3.17 - 10.5.3.22 10.5.3.16/255.255.255.248
4 10.5.3.24 10.5.3.31 10.5.3.25 - 10.5.3.30 10.5.3.24/255.255.255.248
5 10.5.3.32 10.5.3.39 10.5.3.33 - 10.5.3.38 10.5.3.32/255.255.255.248
6 10.5.3.40 10.5.3.47 10.5.3.41 - 10.5.3.46 10.5.3.40/255.255.255.248
7 10.5.3.48 10.5.3.55 10.5.3.49 - 10.5.3.54 10.5.3.48/255.255.255.248
8 10.5.3.56 10.5.3.63 10.5.3.57 - 10.5.3.62 10.5.3.56/255.255.255.248
9 10.5.3.64 10.5.3.71 10.5.3.65 - 10.5.3.70 10.5.3.64/255.255.255.248
10 10.5.3.72 10.5.3.79 10.5.3.73 - 10.5.3.78 10.5.3.72/255.255.255.248
11 10.5.3.80 10.5.3.87 10.5.3.81 - 10.5.3.86 10.5.3.80/255.255.255.248
12 10.5.3.88 10.5.3.95 10.5.3.89 - 10.5.3.94 10.5.3.88/255.255.255.248
13 10.5.3.96 10.5.3.103 10.5.3.97 - 10.5.3.102 10.5.3.96/255.255.255.248
14 10.5.3.104 10.5.3.111 10.5.3.105 - 10.5.3.110 10.5.3.104/255.255.255.248
15 10.5.3.112 10.5.3.119 10.5.3.113 - 10.5.3.118 10.5.3.112/255.255.255.248
16 10.5.3.120 10.5.3.127 10.5.3.121 - 10.5.3.126 10.5.3.120/255.255.255.248
17 10.5.3.128 10.5.3.135 10.5.3.129 - 10.5.3.134 10.5.3.128/255.255.255.248
18 10.5.3.136 10.5.3.143 10.5.3.137 - 10.5.3.142 10.5.3.136/255.255.255.248
19 10.5.3.144 10.5.3.151 10.5.3.145 - 10.5.3.150 10.5.3.144/255.255.255.248
20 10.5.3.152 10.5.3.159 10.5.3.153 - 10.5.3.158 10.5.3.152/255.255.255.248
21 10.5.3.160 10.5.3.167 10.5.3.161 - 10.5.3.166 10.5.3.160/255.255.255.248
22 10.5.3.168 10.5.3.175 10.5.3.169 - 10.5.3.174 10.5.3.168/255.255.255.248
23 10.5.3.176 10.5.3.183 10.5.3.177 - 10.5.3.182 10.5.3.176/255.255.255.248
24 10.5.3.184 10.5.3.191 10.5.3.185 - 10.5.3.190 10.5.3.184/255.255.255.248
25 10.5.3.192 10.5.3.199 10.5.3.193 - 10.5.3.198 10.5.3.192/255.255.255.248
26 10.5.3.200 10.5.3.207 10.5.3.201 - 10.5.3.206 10.5.3.200/255.255.255.248
27 10.5.3.208 10.5.3.215 10.5.3.209 - 10.5.3.214 10.5.3.208/255.255.255.248
28 10.5.3.216 10.5.3.223 10.5.3.217 - 10.5.3.222 10.5.3.216/255.255.255.248
29 10.5.3.224 10.5.3.231 10.5.3.225 - 10.5.3.230 10.5.3.224/255.255.255.248
30 10.5.3.232 10.5.3.239 10.5.3.233 - 10.5.3.238 10.5.3.232/255.255.255.248
31 10.5.3.240 10.5.3.247 10.5.3.241 - 10.5.3.246 10.5.3.240/255.255.255.248
32 10.5.3.248 10.5.3.255 10.5.3.249 - 10.5.3.254 10.5.3.248/255.255.255.248

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Subnetting a Class C Address into 8 x 30 address subnets

Subnetting a Class C Address into
8 x 30 address subnets