Quick subnets page, because I need a quick reference when I'm tired...
IPv4 subnets
| 2nd/a |
3rd/b |
4th/c |
Subs |
x |
Hosts |
octet subnet |
binary |
num of bits |
| /08 |
/16 (65536) |
/24 (256) |
(1 |
x |
256) |
.0 |
0000 0000 |
0 |
| /09 |
/17 (32768) |
/25 (128) |
(2 |
x |
128) |
.128 |
1000 0000 |
1 |
| /10 |
/18 (16384) |
/26 (64) |
(4 |
x |
64) |
.192 |
1100 0000 |
2 |
| /11 |
/19 (8192) |
/27 (32) |
(8 |
x |
32) |
.224 |
1110 0000 |
3 |
| /12 |
/20 (4096) |
/28 (16) |
(16 |
x |
16) |
.240 |
1111 0000 |
4 |
| /13 |
/21 (2048) |
/29 (8) |
(32 |
x |
8) |
.248 |
1111 1000 |
5 |
| /14 |
/22 (1024) |
/30 (4) |
(64 |
x |
4) |
.252 |
1111 1100 |
6 |
| /15 |
/23 (512) |
/31 (2) |
(128 |
x |
2) |
.254 |
1111 1110 |
7 |
|
|
/32 (1) |
(256 |
x |
1) |
.255 |
1111 1111 |
8 |
ipV4 Mind calc exercises
/11 - /19 - /27 - .224 - blocks of 32
32
64
96
128
160
192
224
subnets and hosts
| host bits |
stolen bits |
subnets |
hosts (-2) |
| 8 |
0 |
1 |
254 (-2) |
| 7 |
1 |
2 |
128 (-2) |
| 6 |
2 |
4 |
64 (-2) |
| 5 |
3 |
8 |
32 (-2) |
| 4 |
4 |
16 |
16 (-2) |
| 3 |
5 |
32 |
8 (-2) |
| 2 |
6 |
64 |
4 (-2) |
| 1 |
7 |
128 |
2 (-2) |
| 0 |
8 |
256 |
1 (-2) |
shortcut for calculating
example - 172.25.0.0/24
- what is interesting octet (last octet to contain) 1 in subnet mask - 3rd
- what is block size that we count by => 256 - value in subnet masks interesting octet = 256-255 = 1 ... we count by 1 in interesting octet for subnets (172.25.0.0/24, 172.25.1.0/24, 172.25.2.0/24 (etc)
- What are the usable ranges of ipaddrs? - 253