Monday, February 23, 2009

All possible netmasks expanded


Netmask Netmask (binary) CIDR Notes
255.255.255.255 11111111.11111111.11111111.11111111 /32 Host (single address)
255.255.255.254 11111111.11111111.11111111.11111110 /31 Unuseable
255.255.255.252 11111111.11111111.11111111.11111100 /30 2 useable
255.255.255.248 11111111.11111111.11111111.11111000 /29 6 useable
255.255.255.240 11111111.11111111.11111111.11110000 /28 14 useable
255.255.255.224 11111111.11111111.11111111.11100000 /27 30 useable
255.255.255.192 11111111.11111111.11111111.11000000 /26 62 useable
255.255.255.128 11111111.11111111.11111111.10000000 /25 126 useable
255.255.255.0 11111111.11111111.11111111.00000000 /24 "Class C" 254 useable



Netmask 255.255.255.0 /24 (11111111.11111111.11111111.00000000)
1 subnet
LOW IP HI IP
x.x.x.0 x.x.x.255

Netmask 255.255.255.128 /25 (11111111.11111111.11111111.10000000)
2 subnets
LOW IP HI IP
x.x.x.0 x.x.x.127
x.x.x.128 x.x.x.255

Netmask 255.255.255.192 /26 (11111111.11111111.11111111.11000000)
4 subnets
x.x.x.0 x.x.x.63
x.x.x.64 x.x.x.127
x.x.x.128 x.x.x.191
x.x.x.192 x.x.x.255

Netmask 255.255.255.224 /27 (11111111.11111111.11111111.11100000)
8 subnets
x.x.x.0 x.x.x.31
x.x.x.32 x.x.x.63
x.x.x.64 x.x.x.95
x.x.x.96 x.x.x.127
x.x.x.128 x.x.x.159
x.x.x.160 x.x.x.191
x.x.x.192 x.x.x.223
x.x.x.224 x.x.x.255

Netmask 255.255.255.240 /28 (11111111.11111111.11111111.11110000)
16 subnets
x.x.x.0 x.x.x.15
x.x.x.16 x.x.x.31
x.x.x.32 x.x.x.47
x.x.x.48 x.x.x.63
x.x.x.64 x.x.x.79
x.x.x.80 x.x.x.95
x.x.x.96 x.x.x.111
x.x.x.112 x.x.x.127
x.x.x.128 x.x.x.143
x.x.x.144 x.x.x.159
x.x.x.160 x.x.x.175
x.x.x.176 x.x.x.191
x.x.x.192 x.x.x.207
x.x.x.208 x.x.x.223
x.x.x.224 x.x.x.239
x.x.x.240 x.x.x.255

Netmask 255.255.255.248 /29 (11111111.11111111.11111111.11111000)
32 subnets
x.x.x.0 x.x.x.7
x.x.x.8 x.x.x.15
x.x.x.16 x.x.x.23
x.x.x.24 x.x.x.31
x.x.x.32 x.x.x.39
x.x.x.40 x.x.x.47
x.x.x.48 x.x.x.55
x.x.x.56 x.x.x.63
x.x.x.64 x.x.x.71
x.x.x.72 x.x.x.79
x.x.x.80 x.x.x.87
x.x.x.88 x.x.x.95
x.x.x.96 x.x.x.103
x.x.x.104 x.x.x.111
x.x.x.112 x.x.x.119
x.x.x.120 x.x.x.127
x.x.x.128 x.x.x.135
x.x.x.136 x.x.x.143
x.x.x.144 x.x.x.151
x.x.x.152 x.x.x.159
x.x.x.160 x.x.x.167
x.x.x.168 x.x.x.175
x.x.x.176 x.x.x.183
x.x.x.184 x.x.x.191
x.x.x.192 x.x.x.199
x.x.x.200 x.x.x.207
x.x.x.208 x.x.x.215
x.x.x.216 x.x.x.223
x.x.x.224 x.x.x.231
x.x.x.232 x.x.x.239
x.x.x.240 x.x.x.247
x.x.x.248 x.x.x.255

Netmask 255.255.255.252 /30 (11111111.11111111.11111111.11111100)
64 subnets
LOW IP HI IP
x.x.x.0 x.x.x.3
x.x.x.4 x.x.x.7
x.x.x.8 x.x.x.11
x.x.x.12 x.x.x.15
x.x.x.16 x.x.x.19
x.x.x.20 x.x.x.23
x.x.x.24 x.x.x.27
x.x.x.28 x.x.x.31
x.x.x.32 x.x.x.35
x.x.x.36 x.x.x.39
x.x.x.40 x.x.x.43
x.x.x.44 x.x.x.47
x.x.x.48 x.x.x.51
x.x.x.52 x.x.x.55
x.x.x.56 x.x.x.59
x.x.x.60 x.x.x.63
x.x.x.64 x.x.x.67
x.x.x.68 x.x.x.71
x.x.x.72 x.x.x.75
x.x.x.76 x.x.x.79
x.x.x.80 x.x.x.83
x.x.x.84 x.x.x.87
x.x.x.88 x.x.x.91
x.x.x.92 x.x.x.95
x.x.x.96 x.x.x.99
x.x.x.100 x.x.x.103
x.x.x.104 x.x.x.107
x.x.x.108 x.x.x.111
x.x.x.112 x.x.x.115
x.x.x.116 x.x.x.119
x.x.x.120 x.x.x.123
x.x.x.124 x.x.x.127
x.x.x.128 x.x.x.131
x.x.x.132 x.x.x.135
x.x.x.136 x.x.x.139
x.x.x.140 x.x.x.143
x.x.x.144 x.x.x.147
x.x.x.148 x.x.x.151
x.x.x.152 x.x.x.155
x.x.x.156 x.x.x.159
x.x.x.160 x.x.x.163
x.x.x.164 x.x.x.167
x.x.x.168 x.x.x.171
x.x.x.172 x.x.x.175
x.x.x.176 x.x.x.179
x.x.x.180 x.x.x.183
x.x.x.184 x.x.x.187
x.x.x.188 x.x.x.191
x.x.x.192 x.x.x.195
x.x.x.196 x.x.x.199
x.x.x.200 x.x.x.203
x.x.x.204 x.x.x.207
x.x.x.208 x.x.x.211
x.x.x.212 x.x.x.215
x.x.x.216 x.x.x.219
x.x.x.220 x.x.x.223
x.x.x.224 x.x.x.227
x.x.x.228 x.x.x.231
x.x.x.232 x.x.x.235
x.x.x.236 x.x.x.239
x.x.x.240 x.x.x.243
x.x.x.244 x.x.x.247
x.x.x.248 x.x.x.251
x.x.x.252 x.x.x.255

net mask:

1111 11 00 == 252

Pozar's two-bit(tm) addressing

4-bit m m m m
2-bit m m
(.1) 0 0 0 0 0 0 0 1 (.2) 0 0 0 0 0 0 1 0
(.17) 0 0 0 1 0 0 0 1 (.18) 0 0 0 1 0 0 1 0
(.33) 0 0 1 0 0 0 0 1 (.34) 0 0 1 0 0 0 1 0
(.49) 0 0 1 1 0 0 0 1 (.50) 0 0 1 1 0 0 1 0
(.65) 0 1 0 0 0 0 0 1 (.66) 0 1 0 0 0 0 1 0
(.129) 1 0 0 0 0 0 0 1 (.130) 1 0 0 0 0 0 1 0
(.193) 1 1 0 0 0 0 0 1 (.194) 1 1 0 0 0 0 1 0
(.225) 1 1 1 0 0 0 0 1 (.226) 1 1 1 0 0 0 1 0



CIDR: Classless Inter-Domain Routing -- Standard Boundaries

(inverse mask)
Netmask bits # IPs # C's source-wildcard

255.255.255.255 /32 1 < 0.0.0.0
255.255.255.254 /31 2 < 0.0.0.1
255.255.255.252 /30 4 < 0.0.0.3
255.255.255.248 /29 8 < 0.0.0.7
255.255.255.240 /28 16 < 0.0.0.15
255.255.255.224 /27 32 < 0.0.0.31
255.255.255.192 /26 64 < 0.0.0.63
255.255.255.128 /25 128 < 0.0.0.127
255.255.255.0 /24 256 1 0.0.0.255
255.255.254.0 /23 512 2 0.0.1.255
255.255.252.0 /22 1024 4 0.0.3.255
255.255.248.0 /21 2048 8 0.0.7.255
255.255.240.0 /20 4096 16 0.0.15.255
255.255.224.0 /19 8192 32 0.0.31.255
255.255.192.0 /18 16384 64 0.0.63.255
255.255.128.0 /17 32768 128 0.0.127.255
255.255.0.0 /16 65536 256 0.0.255.255
255.254.0.0 /15 131072 512 0.1.255.255
255.252.0.0 /14 262144 1024 0.3.255.255
255.248.0.0 /13 524288 2048 0.7.255.255
255.240.0.0 /12 1048576 4096 0.15.255.255
255.224.0.0 /11 2097152 8192 0.31.255.255
255.192.0.0 /10 4194304 16384 0.63.255.255
255.128.0.0 /9 8388608 32768 0.127.255.255
255.0.0.0 /8 16777216 65536 0.255.255.255
254.0.0.0 /7 33554432 131072 1.255.255.255
252.0.0.0 /6 67108864 262144 3.255.255.255
248.0.0.0 /5 134217.72K 524288 7.255.255.255
240.0.0.0 /4 268435.44K 1048576 15.255.255.255
224.0.0.0 /3 536870.88K 2097152 31.255.255.255
192.0.0.0 /2 1073741.7K 4194304 63.255.255.255
128.0.0.0 /1 2147483.4K 8388608 127.255.255.255
0.0.0.0 /0 4294966.8K 16777216 255.255.255.255

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Here's some general rules about how this allocation works. Keep in mind that
all of these "masks" are really based on binary AND/OR masking, thus a
decimal "255" is binary 11111111 and a decimal "0" is binary "00000000".
Here's a little table in binary which may be of help:

255.255.255.255 /32 11111111.11111111.11111111.11111111
255.255.255.254 /31 11111111.11111111.11111111.11111110
255.255.255.252 /30 11111111.11111111.11111111.11111100
255.255.255.248 /29 11111111.11111111.11111111.11111000
255.255.255.240 /28 11111111.11111111.11111111.11110000
255.255.255.224 /27 11111111.11111111.11111111.11100000
255.255.255.192 /26 11111111.11111111.11111111.11000000
255.255.255.128 /25 11111111.11111111.11111111.10000000
255.255.255.0 /24 11111111.11111111.11111111.00000000
255.255.254.0 /23 11111111.11111111.11111110.00000000
255.255.252.0 /22 11111111.11111111.11111100.00000000
255.255.248.0 /21 11111111.11111111.11111000.00000000
255.255.240.0 /20 11111111.11111111.11110000.00000000
255.255.224.0 /19 11111111.11111111.11100000.00000000
255.255.192.0 /18 11111111.11111111.11000000.00000000
255.255.128.0 /17 11111111.11111111.10000000.00000000
255.255.0.0 /16 11111111.11111111.00000000.00000000
... etc ...

A /32 is an allocation of 1 IP, and there is 256 /32's in a /24.
A /31 is an allocation of 2 IP's, and there is 128 /31's in a /24.
A /30 is an allocation of 4 IP's, and there is 64 /30's in a /24.
A /29 is an allocation of 8 IP's, and there is 32 /29's in a /24.
A /28 is an allocation of 16 IP's, and there is 16 /28's in a /24.
A /27 is an allocation of 32 IP's, and there is 8 /27's in a /24.
A /26 is an allocation of 64 IP's, and there is 4 /26's in a /24.
A /25 is an allocation of 128 IP's, and there is 2 /25's in a /24.
A /24 is an allocation of 256 IP's, and there is 1 /24 in a /24.

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Starting "Network" IP address of Subnetted /24's (last octet value):
NOTE: *0 - Zero subnet may not functional on ALL CPE types

/32: Any IP is an individual /32.
/31: IP evenly divisible by 2. (e.g. *0,2,4,6,8,10,12,14,16,18 ... 252,254)
/30: IP evenly divisible by 4. (e.g. *0,4,8,12,16,20,24,28,32, ... 248,252)
/29: IP evenly divisible by 8. (e.g. *0,8,16,24,32,40,48,56,64, ... 240,248)
/28: IP evenly divisible by 16. (e.g. *0,16,32,48,64,80,96,112, ... 224,240)
/27: IP evenly divisible by 32. (e.g. *0,32,64,96,128,160,192,224)
/26: IP evenly divisible by 64. (e.g. *0,64,128,192)

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