Subnetting Made Slightly Easier !
| 27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
Place |
| 128 |
64 |
32 |
16 |
8 |
4 |
2 |
1 |
Decimal Place Value |
| 1 |
0 |
1 |
1 |
0 |
1 |
1 |
1 |
Binary Value |
The total of 128 + 32 + 16 + 4 + 2 + 1 = 183.
Each power of 2 position value doubles the previous one. Each place value represents a power of 2 result for the binary value.
IP addresses are organized by classes: Class A, Class B, and Class C. defines the range and amount of hosts included with each network.
| Class |
Byte1 |
Byte2 |
Byte3 |
Byte4 |
| A |
NETWORK |
HOST |
HOST |
HOST |
| B |
NETWORK |
NETWORK |
HOST |
HOST |
| C |
NETWORK |
NETWORK |
NETWORK |
HOST |
| Address Class |
From |
To |
Host IDS |
Net IDs |
Bits for Subnet Mask |
Subnet Mask |
Class A /8 to represent the number of bits used by the network address. |
1 |
126 |
126 |
16,777,214 |
11111111 00000000 00000000 00000000 |
255.0.0.0 |
Class B /16 to represent the number of bits used by the network address. |
128 |
191 |
16,384 |
65,534 |
11111111 11111111 00000000 00000000 |
255.255.0.0 |
Class C /24 to represent the number of bits used by the network address. |
192 |
223 |
2,097,152 |
254 |
11111111 11111111 11111111 00000000 |
255.255.255.0 |
Determining the Number of Bits Required for Subnetting
| Number of Bits for the Subnet ID |
Number of Subnets |
| 1 |
2 |
| 2 |
4 |
| 3 |
8 |
| 4 |
16 |
| 5 |
32 |
| 6 |
64 |
| 7 |
128 |
| 8 |
256 |
| 9 |
512 |
| 10 |
1024 |
| 11 |
2048 |
| 12 |
4096 |
Class
A Table
| Subnets |
Binary |
Mask |
Hosts |
| 0 |
10000000 |
255.128.0.0 |
Invalid subnet |
| 2 |
11000000 |
255.192.0.0 |
4,194,302 |
| 6 |
11100000 |
255.224.0.0 |
2,097,150 |
| 14 |
11110000 |
255.240.0.0 |
1,048,574 |
| 30 |
11111000 |
255.248.0.0 |
524,286 |
| 62 |
11111100 |
255.252.0.0 |
262,142 |
| 126 |
11111110 |
255.254.0.0 |
131,070 |
| 254 |
11111111 |
255.255.0.0 |
65,534 |
Class B Table
| Subnets |
Binary |
Mask |
Hosts |
| 0 |
10000000 |
255..255.128.0 |
Invalid subnet |
| 2 |
11000000 |
255.255.192.0 |
16,382 |
| 6 |
11100000 |
255.255.224.0 |
8,190 |
| 14 |
11110000 |
255.255.240.0 |
4,094 |
| 30 |
11111000 |
255.255.248.0 |
2,046 |
| 62 |
11111100 |
255.255.252.0 |
1,022 |
| 126 |
11111110 |
255.255.254.0 |
510 |
| 254 |
11111111 |
255.255.255.0 |
254 |
Class C Table
| Subnets |
Binary |
Mask |
Hosts |
| 0 |
10000000 |
255.255.255.128 |
Invalid subnet |
| 2 |
11000000 |
255.255.255.192 |
62 |
| 6 |
11100000 |
255.255.255.224 |
30 |
| 14 |
11110000 |
255.255.255.240 |
14 |
| 30 |
11111000 |
255.255.255.248 |
6 |
| 62 |
11111100 |
255.255.255.252 |
2 |
| 126 |
11111110 |
255.255.255.254 |
Invalid subnet |
| 254 |
11111111 |
255.255.255.255 |
Invalid subnet |
All one's or all zero's is not
possible
The network and the
hosts ID can not be all zero, which would indicate the 'Local network', or
cannot all be one, which would indicate the broadcast address.
CALCULATING SUBNET MASK, SUBNET IDS, AND NUMBER OF SUBNETS
| Position Value |
64 |
32 |
16 |
8 |
4 |
2 |
1 |
| Subnet bits |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| Subnets Available |
2 TO POWER OF 2-2 =2 |
2 TO POWER OF 3-2 =6 |
2 TO POWER OF 4-2 =14 |
2 TO POWER OF 5-2 =30 |
2 TO POWER OF 6-2 =62 |
2 TO POWER OF 7-2 =126 |
2 TO POWER OF 8-2 =254 |
| Subnet Mask |
128+64 192 |
192+32 224 |
224+16 240 |
240+8 248 |
248+4 252 |
252+2 254 |
254+1 255 |
| Host bits |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
I HOPE THESE TABLES MADE SUBNETTING SLIGHTLY EASIER FOR YOU ?
ME? WELL I AM STILL GETTING THE HANG OF IT !