Hi guys, ive created this small txt file that ive used for revision, im posting it here because you might find it useful!
Use this table for reference, remember there are 32 bits in an IPv4 IP Address!
/0 = 0 ( 00000000.00000000.00000000.00000000 ) or 0.0.0.0
/1 = 128 ( 10000000.00000000.00000000.00000000 ) or 128.0.0.0
/2 = 192 ( 11000000.00000000.00000000.00000000 ) or 192.0.0.0
/3 = 224 ( 11100000.00000000.00000000.00000000 ) or 224.0.0.0
/4 = 240 ( 11110000.00000000.00000000.00000000 ) or 240.0.0.0
/5 = 248 ( 11111000.00000000.00000000.00000000 ) or 248.0.0.0
/6 = 252 ( 11111100.00000000.00000000.00000000 ) or 252.0.0.0
/7 = 254 ( 11111110.00000000.00000000.00000000 ) or 254.0.0.0
/8 = 0 ( 11111111.00000000.00000000.00000000 ) or 255.0.0.0
/9 = 128 ( 11111111.10000000.00000000.00000000 ) or 255.128.0.0
/10 = 192 ( 11111111.11000000.00000000.00000000 ) or 255.192.0.0
/11 = 224 ( 11111111.11100000.00000000.00000000 ) or 255.224.0.0
/12 = 240 ( 11111111.11110000.00000000.00000000 ) or 255.240.0.0
/13 = 248 ( 11111111.11111000.00000000.00000000 ) or 255.248.0.0
/14 = 252 ( 11111111.11111100.00000000.00000000 ) or 255.252.0.0
/15 = 254 ( 11111111.11111110.00000000.00000000 ) or 255.254.0.0
/16 = 0 ( 11111111.11111111.00000000.00000000 ) or 255.255.0.0
/17 = 128 ( 11111111.11111111.10000000.00000000 ) or 255.255.128.0
/18 = 192 ( 11111111.11111111.11000000.00000000 ) or 255.255.192.0
/19 = 224 ( 11111111.11111111.11100000.00000000 ) or 255.255.224.0
/20 = 240 ( 11111111.11111111.11110000.00000000 ) or 255.255.240.0
/21 = 248 ( 11111111.11111111.11111000.00000000 ) or 255.255.248.0
/22 = 252 ( 11111111.11111111.11111100.00000000 ) or 255.255.252.0
/23 = 254 ( 11111111.11111111.11111110.00000000 ) or 255.255.254.0
/24 = 255 ( 11111111.11111111.11111111.00000000 ) or 255.255.255.0
/25 = 128 ( 11111111.11111111.11111111.10000000 ) or 255.255.255.128
/26 = 192 ( 11111111.11111111.11111111.11000000 ) or 255.255.255.192
/27 = 224 ( 11111111.11111111.11111111.11100000 ) or 255.255.255.224
/28 = 240 ( 11111111.11111111.11111111.11110000 ) or 255.255.255.240
/29 = 248 ( 11111111.11111111.11111111.11111000 ) or 255.255.255.248
/30 = 252 ( 11111111.11111111.11111111.11111100 ) or 255.255.255.252
/31 = 254 ( 11111111.11111111.11111111.11111110 ) or 255.255.255.254
/32 = 255 ( 11111111.11111111.11111111.11111111 ) or 255.255.255.255
Examples: (Follow them to calculate your own for practice)
Rules:
1. there are a total of 256 addresses per octet
2. you don't have to subtract two when determining subnets (except for a few specific cases)
3. You cannot use all 1's and all 0's for IP Addresses (e.g. - 256-2 = 254)
an example: 255.255.0.0 (take 2 addresses away so 256 x 256 -2 = 65534
4. In a subnet, only one octet may carry a custom number, all others must
be either 255 or 0
Standard Example IPv4 Examples:
(Class A Standard) 256 x 256 x 256 -2 = 16777214 Hosts Available
(Class B Standard) 256 x 256 -2 = 65534 Hosts Available
(Class C Standard) 256 -2 = 254 Hosts Available
CIDR (Classless Inter-Domain Routing) examples:
1)
00001010.00000000.00000000.00000000 = ( 10.0.0.0 )
256 - 10 = 246
256 - 0 = 256
256 - 0 = 256
256 - 0 = 256
246 x 256 x 256 x 256 = 4127195136 - 2 = 4127195134 Hosts
2)
11111110.00000000.00000000.00000000 = ( 254.0.0.0 )
256 - 254 = 2
256 - 0 = 256
256 - 0 = 256
256 - 0 = 256
2 x 256 x 256 x 256 = 33554432 - 2 = 33554430 Hosts
3)
10000000.00000000.00000000.00000000 = ( 128.0.0.0 )
256 - 128 = 128
256 - 0 = 256
256 - 0 = 256
256 - 0 = 256
128 x 256 x 256 x 256 = 2147483648 -2 = 2147483646 Hosts
Formula:
LEGEND:
n = custom octet
v = Value after subtraction
octet = other octet in the range, carry out the same equation with octet
tHosts = Theoretical Maximum hosts
vHosts = Value of real Hosts
256 = a 0 address range (All other octets to the right of the custom octet
must be a 0 to accommodate for the IP addresses.
255 = lock out address
-2 = addresses that cannot be used because 0 is a wildcard address and 255
is the lock out address.
x = Multiply by
Examples:
n.0.0.0 (Unclassified)
255.n.0.0 (Class A Range)
255.255.n.0 (Class B Range)
255.255.255.n (Class C Range)
Examples:
256 - n = v
octet
octet
octet
n x octet x octet x octet = tHosts -2 = vHosts
Hope this guide was useful! ~ Wedge 1988 ~
