Subnetting Calculation

Subnetting allows creating smaller network (sub networks or subnets) inside a large network by borrowing bits from the Host ID portion of the address. The borrowed bits can be used to create additional networks, resulting in smaller-sized networks. This can help to reduce wastage, improve network performance, effective isolation and easier administration.

A subnet mask is the representation of the network portion of an address. It is also made up of 32 bits with all the bits that represent the network portion being marked as 1s and the other parts marked as 0s.

For a Class C IPv4 address, the first three octets are used to represent the network part and the last octet is used to represent the host part. 

 

Subnetting Calculation

In term of private addressing scheme, UTeM network is class C private addressing scheme which is 192.168.0.0 that will be provided to 30 departments.

The default subnet mask is: 255.255.255.0  or  11111111 11111111 11111111 00000000 

 

Given 30 departments, to avoid wastage in IPv4 address,

v  The number of subnet should be at least 30 for support, where 2⁵=32 subnets (≥ 30). Thus, there will be 5 bits borrowed to create additional networks.

v  Since the first and the last IPv4 addresses in each subnet block are used to represent its network address and the broadcast address, they cannot be used to configure the devices inside your network. The number of hosts = (2³ - 2) = (8 - 2) = 6 hosts  where 3 bits is remaining in the host field.

 

So, the network address with its prefix length will be: 192.168.0.0/29. The subnet mask determined : 255.255.255.248  or 11111111 11111111 11111111 11111000

The network 192.168.0.0 is divided into 32 subnets, each subnet has 8 total IPv4 addresses and 6 usable IPv4 addresses. Two IPv4 addresses are used in each subnet to represent the network address and the broadcast address.

 

#	Network Address	Available host address range per subnet	Broadcast Address
1	192.168.0.0	192.168.0.1   - 192.168.0.6	192.168.0.7
2	192.168.0.8	192.168.0.9   - 192.168.0.14	192.168.0.15
3	192.168.0.16	192.168.0.17  - 192.168.0.22	192.168.0.23
4	192.168.0.24	192.168.0.25   - 192.168.0.30	192.168.0.31
5	192.168.0.32	192.168.0.33  - 192.168.0.38	192.168.0.39
6	192.168.0.40	192.168.0.41   - 192.168.0.46	192.168.0.47
7	192.168.0.48	192.168.0.49   - 192.168.0.54	192.168.0.55
8	192.168.0.56	192.168.0.57   - 192.168.0.62	192.168.0.63
9	192.168.0.64	192.168.0.65   - 192.168.0.70	192.168.0.71
10	192.168.0.72	192.168.0.73   - 192.168.0.78	192.168.0.79
11	192.168.0.80	192.168.0.81   - 192.168.0.86	192.168.0.87
12	192.168.0.88	192.168.0.89   - 192.168.0.94	192.168.0.95
13	192.168.0.96	192.168.0.97   - 192.168.0.102	192.168.0.103
14	192.168.0.104	192.168.0.105   - 192.168.0.110	192.168.0.111
15	192.168.0.112	192.168.0.113   - 192.168.0.118	192.168.0.119
16	192.168.0.120	192.168.0.121   - 192.168.0.126	192.168.0.127
17	192.168.0.128	192.168.0.129   - 192.168.0.134	192.168.0.135
18	192.168.0.136	192.168.0.137   - 192.168.0.142	192.168.0.143
19	192.168.0.144	192.168.0.145   - 192.168.0.150	192.168.0.151
20	192.168.0.152	192.168.0.153   - 192.168.0.158	192.168.0.159
21	192.168.0.160	192.168.0.161   - 192.168.0.166	192.168.0.167
22	192.168.0.168	192.168.0.169   - 192.168.0.174	192.168.0.175
23	192.168.0.176	192.168.0.177   - 192.168.0.186	192.168.0.187
24	192.168.0.184	192.168.0.185   - 192.168.0.190	192.168.0.191
25	192.168.0.192	192.168.0.193   - 192.168.0.198	192.168.0.199
26	192.168.0.200	192.168.0.201   - 192.168.0.206	192.168.0.207
27	192.168.0.208	192.168.0.209   - 192.168.0.214	192.168.0.215
28	192.168.0.216	192.168.0.217   - 192.168.0.222	192.168.0.223
29	192.168.0.224	192.168.0.225   - 192.168.0.230	192.168.0.231
30	192.168.0.232	192.168.0.233   - 192.168.0.239	192.168.0.240
31	192.168.0.241	192.168.0.242   - 192.168.0.246	192.168.0.247
32	192.168.0.248	192.168.0.249   - 192.168.0.254	192.168.0.255

 

Table 1 :  32 subnets obtained from 5-bit subnetting for class C network.

 

From the table above, it is determined that :

The network address assigned to IT Center is 192.168.0.80 (11^th available subnet).

 In the 11^th  available subnet, among the network address available,

 

The 3^rd available address for Ulearn System Server is 192.168.0.83.