Subnetting - Again

Common errors - use of addresses OUTSIDE of the allocated addressing scheme.



e.g. Use addresses from the 192.168.100.0 /24 range to create FOUR equally sized subnetworks.

What is the length of an IPv4 address? 32 bits.

The SUBNET MASK (SM) exists to show us how many bits we have to work with. It gives us an idea of the SIZE of the pool of addresses we have been given.

Here the SM is 24 which means we only have the last 8 bits to work with (because 24 + 8 = 32).

Now let us write the address pool in binary. We will use colours to illustrate the sections of the address.

The part we cannot use will be RED
The part we can use will be GREEN
The part for our own subnetting will be BLUE

11000000. 10101000. 010101000. 00000000

This shows 24 bits we cannot use and 8 bits we can use.

If you have used the addresses 192.168.101.1 etc. then you have violated the addressing range - write this out in binary.....

11000000. 10101000. 010101001. 00000001

The last bit in the third octet is now a binary ONE and we are not allowed to use these bits.

We can only work with the  GREEN bits. There are  8 bits available here. These are ALL we are allowed to work with.

For this assignment, the use of subnet zero is allowed therefore we can have a subnetwork that consists of all zeros.

The first section requested that you create FOUR equally sized subnetworks.

You have 8 bits. 28 = 256

This gives a possible range (in decimal) from 0 to 255.
0 0 0 0 0 0 0 0
0
0 0 0 0 0 0 0 1
1
0 0 0 0 0 0 1 0
2
0 0 0 0 0 0 1 1
3
0 0 0 0 0 1 0 0
4
0 0 0 0 0 1 0 1
5
0 0 0 0 0 1 1 0
6
0 0 0 0 0 1 1 1
7
0 0 0 0 1 0 0 0
8
0 0 0 0 1 0 0 1
9
0 0 0 0 1 0 1 0
10
0 0 0 0 1 0 1 1
11
0 0 0 0 1 1 0 0
12
0 0 0 0 1 1 0 1
13
0 0 0 0 1 1 1 0
14
0 0 0 0 1 1 1 1
15
0 0 0 1 0 0 0 0
16
0 0 0 1 0 0 0 1
17
0 0 0 1 0 0 1 0
18
0 0 0 1 0 0 1 1
19
0 0 0 1 0 1 0 0
20
0 0 0 1 0 1 0 1
21
0 0 0 1 0 1 1 0
22
0 0 0 1 0 1 1 1
23
0 0 0 1 1 0 0 0
24
0 0 0 1 1 0 0 1
25
0 0 0 1 1 0 1 0
26
0 0 0 1 1 0 1 1
27
0 0 0 1 1 1 0 0
28
0 0 0 1 1 1 0 1
29
0 0 0 1 1 1 1 0
30
0 0 0 1 1 1 1 1
31
0 0 1 0 0 0 0 0
32
0 0 1 0 0 0 0 1
33
0 0 1 0 0 0 1 0
34
0 0 1 0 0 0 1 1
35
0 0 1 0 0 1 0 0
36
0 0 1 0 0 1 0 1
37
0 0 1 0 0 1 1 0
38
0 0 1 0 0 1 1 1
39
0 0 1 0 1 0 0 0
40
0 0 1 0 1 0 0 1
41
0 0 1 0 1 0 1 0
42
0 0 1 0 1 0 1 1
43
0 0 1 0 1 1 0 0
44
0 0 1 0 1 1 0 1
45
0 0 1 0 1 1 1 0
46
0 0 1 0 1 1 1 1
47
0 0 1 1 0 0 0 0
48
0 0 1 1 0 0 0 1
49
0 0 1 1 0 0 1 0
50
0 0 1 1 0 0 1 1
51
0 0 1 1 0 1 0 0
52
0 0 1 1 0 1 0 1
53
0 0 1 1 0 1 1 0
54
0 0 1 1 0 1 1 1
55
0 0 1 1 1 0 0 0
56
0 0 1 1 1 0 0 1
57
0 0 1 1 1 0 1 0
58
0 0 1 1 1 0 1 1
59
0 0 1 1 1 1 0 0
60
0 0 1 1 1 1 0 1
61
0 0 1 1 1 1 1 0
62
0 0 1 1 1 1 1 1
63
0 1 0 0 0 0 0 0
64
0 1 0 0 0 0 0 1
65
0 1 0 0 0 0 1 0
66
0 1 0 0 0 0 1 1
67
0 1 0 0 0 1 0 0
68
0 1 0 0 0 1 0 1
69
0 1 0 0 0 1 1 0
70
0 1 0 0 0 1 1 1
71
0 1 0 0 1 0 0 0
72
0 1 0 0 1 0 0 1
73
0 1 0 0 1 0 1 0
74
0 1 0 0 1 0 1 1
75
0 1 0 0 1 1 0 0
76
0 1 0 0 1 1 0 1
77
0 1 0 0 1 1 1 0
78
0 1 0 0 1 1 1 1
79
0 1 0 1 0 0 0 0
80
0 1 0 1 0 0 0 1
81
0 1 0 1 0 0 1 0
82
0 1 0 1 0 0 1 1
83
0 1 0 1 0 1 0 0
84
0 1 0 1 0 1 0 1
85
0 1 0 1 0 1 1 0
86
0 1 0 1 0 1 1 1
87
0 1 0 1 1 0 0 0
88
0 1 0 1 1 0 0 1
89
0 1 0 1 1 0 1 0
90
0 1 0 1 1 0 1 1
91
0 1 0 1 1 1 0 0
92
0 1 0 1 1 1 0 1
93
0 1 0 1 1 1 1 0
94
0 1 0 1 1 1 1 1
95
0 1 1 0 0 0 0 0
96
0 1 1 0 0 0 0 1
97
0 1 1 0 0 0 1 0
98
0 1 1 0 0 0 1 1
99
0 1 1 0 0 1 0 0
100
0 1 1 0 0 1 0 1
101
0 1 1 0 0 1 1 0
102
0 1 1 0 0 1 1 1
103
0 1 1 0 1 0 0 0
104
0 1 1 0 1 0 0 1
105
0 1 1 0 1 0 1 0
106
0 1 1 0 1 0 1 1
107
0 1 1 0 1 1 0 0
108
0 1 1 0 1 1 0 1
109
0 1 1 0 1 1 1 0
110
0 1 1 0 1 1 1 1
111
0 1 1 1 0 0 0 0
112
0 1 1 1 0 0 0 1
113
0 1 1 1 0 0 1 0
114
0 1 1 1 0 0 1 1
115
0 1 1 1 0 1 0 0
116
0 1 1 1 0 1 0 1
117
0 1 1 1 0 1 1 0
118
0 1 1 1 0 1 1 1
119
0 1 1 1 1 0 0 0
120
0 1 1 1 1 0 0 1
121
0 1 1 1 1 0 1 0
122
0 1 1 1 1 0 1 1
123
0 1 1 1 1 1 0 0
124
0 1 1 1 1 1 0 1
125
0 1 1 1 1 1 1 0
126
0 1 1 1 1 1 1 1
127
1 0 0 0 0 0 0 0
128
1 0 0 0 0 0 0 1
129
1 0 0 0 0 0 1 0
130
1 0 0 0 0 0 1 1
131
1 0 0 0 0 1 0 0
132
1 0 0 0 0 1 0 1
133
1 0 0 0 0 1 1 0
134
1 0 0 0 0 1 1 1
135
1 0 0 0 1 0 0 0
136
1 0 0 0 1 0 0 1
137
1 0 0 0 1 0 1 0
138
1 0 0 0 1 0 1 1
139
1 0 0 0 1 1 0 0
140
1 0 0 0 1 1 0 1
141
1 0 0 0 1 1 1 0
142
1 0 0 0 1 1 1 1
143
1 0 0 1 0 0 0 0
144
1 0 0 1 0 0 0 1
145
1 0 0 1 0 0 1 0
146
1 0 0 1 0 0 1 1
147
1 0 0 1 0 1 0 0
148
1 0 0 1 0 1 0 1
149
1 0 0 1 0 1 1 0
150
1 0 0 1 0 1 1 1
151
1 0 0 1 1 0 0 0
152
1 0 0 1 1 0 0 1
153
1 0 0 1 1 0 1 0
154
1 0 0 1 1 0 1 1
155
1 0 0 1 1 1 0 0
156
1 0 0 1 1 1 0 1
157
1 0 0 1 1 1 1 0
158
1 0 0 1 1 1 1 1
159
1 0 1 0 0 0 0 0
160
1 0 1 0 0 0 0 1
161
1 0 1 0 0 0 1 0
162
1 0 1 0 0 0 1 1
163
1 0 1 0 0 1 0 0
164
1 0 1 0 0 1 0 1
165
1 0 1 0 0 1 1 0
166
1 0 1 0 0 1 1 1
167
1 0 1 0 1 0 0 0
168
1 0 1 0 1 0 0 1
169
1 0 1 0 1 0 1 0
170
1 0 1 0 1 0 1 1
171
1 0 1 0 1 1 0 0
172
1 0 1 0 1 1 0 1
173
1 0 1 0 1 1 1 0
174
1 0 1 0 1 1 1 1
175
1 0 1 1 0 0 0 0
176
1 0 1 1 0 0 0 1
177
1 0 1 1 0 0 1 0
178
1 0 1 1 0 0 1 1
179
1 0 1 1 0 1 0 0
180
1 0 1 1 0 1 0 1
181
1 0 1 1 0 1 1 0
182
1 0 1 1 0 1 1 1
183
1 0 1 1 1 0 0 0
184
1 0 1 1 1 0 0 1
185
1 0 1 1 1 0 1 0
186
1 0 1 1 1 0 1 1
187
1 0 1 1 1 1 0 0
188
1 0 1 1 1 1 0 1
189
1 0 1 1 1 1 1 0
190
1 1 1 1 1 1 1 1
191
1 1 0 0 0 0 0 0
192
1 1 0 0 0 0 0 1
193
1 1 0 0 0 0 1 0
194
1 1 0 0 0 0 1 1
195
1 1 0 0 0 1 0 0
196
1 1 0 0 0 1 0 1
197
1 1 0 0 0 1 1 0
198
1 1 0 0 0 1 1 1
199
1 1 0 0 1 0 0 0
200
1 1 0 0 1 0 0 1
201
1 1 0 0 1 0 1 0
202
1 1 0 0 1 0 1 1
203
1 1 0 0 1 1 0 0
204
1 1 0 0 1 1 0 1
205
1 1 0 0 1 1 1 0
206
1 1 0 0 1 1 1 1
207
1 1 0 1 0 0 0 0
208
1 1 0 1 0 0 0 1
209
1 1 0 1 0 0 1 0
210
1 1 0 1 0 0 1 1
211
1 1 0 1 0 1 0 0
212
1 1 0 1 0 1 0 1
213
1 1 0 1 0 1 1 0
214
1 1 0 1 0 1 1 1
215
1 1 0 1 1 0 0 0
216
1 1 0 1 1 0 0 1
217
1 1 0 1 1 0 1 0
218
1 1 0 1 1 0 1 1
219
1 1 0 1 1 1 0 0
220
1 1 0 1 1 1 0 1
221
1 1 0 1 1 1 1 0
222
1 1 0 1 1 1 1 1
223
1 1 1 0 0 0 0 0
224
1 1 1 0 0 0 0 1
225
1 1 1 0 0 0 1 0
226
1 1 1 0 0 0 1 1
227
1 1 1 0 0 1 0 0
228
1 1 1 0 0 1 0 1
229
1 1 1 0 0 1 1 0
230
1 1 1 0 0 1 1 1
231
1 1 1 0 1 0 0 0
232
1 1 1 0 1 0 0 1
233
1 1 1 0 1 0 1 0
234
1 1 1 0 1 0 1 1
235
1 1 1 0 1 1 0 0
236
1 1 1 0 1 1 0 1
237
1 1 1 0 1 1 1 0
238
1 1 1 0 1 1 1 1
239
1 1 1 1 0 0 0 0
240
1 1 1 1 0 0 0 1
241
1 1 1 1 0 0 1 0
242
1 1 1 1 0 0 1 1
243
1 1 1 1 0 1 0 0
244
1 1 1 1 0 1 0 1
245
1 1 1 1 0 1 1 0
246
1 1 1 1 0 1 1 1
247
1 1 1 1 1 0 0 0
248
1 1 1 1 1 0 0 1
249
1 1 1 1 1 0 1 0
250
1 1 1 1 1 0 1 1
251
1 1 1 1 1 1 0 0
252
1 1 1 1 1 1 0 1
253
1 1 1 1 1 1 1 0
254
1 1 1 1 1 1 1 1
255


Up  from zero to decimal 63 are the numbers for the first subnetwork.

We have used 24 (given by our provider) plus TWO BLUE bits = 26 bits in all.

Therefore the range is 192.168.100.0 /26

This encompasses all of the numbers from 192.168.100.0 to 192.168.100.63.

This has used a quarter of our address slice.