CIDR (VLSM)
Classless Inter-Domain Routing (CIDR)
| CIDR | Subnet Mask | Usable IPs |
|---|---|---|
| /0 | 0.0.0.0 | 4,294,967,294 |
| /1 | 128.0.0.0 | 2,147,483,646 |
| /2 | 192.0.0.0 | 1,073,741,822 |
| /3 | 224.0.0.0 | 536,870,910 |
| /4 | 240.0.0.0 | 268,435,454 |
| /5 | 248.0.0.0 | 134,217,726 |
| /6 | 252.0.0.0 | 67,108,862 |
| /7 | 254.0.0.0 | 33,554,430 |
| /8 (A) | 255.0.0.0 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,574 |
| /13 | 255.248.0.0 | 524,286 |
| /14 | 255.252.0.0 | 262,142 |
| /15 | 255.254.0.0 | 131,070 |
| /16 (B) | 255.255.0.0 | 65,534 |
| /17 | 255.255.128.0 | 32,766 |
| /18 | 255.255.192.0 | 16,382 |
| /19 | 255.255.224.0 | 8,190 |
| /20 | 255.255.240.0 | 4,094 |
| /21 | 255.255.248.0 | 2,046 |
| /22 | 255.255.252.0 | 1,022 |
| /23 | 255.255.254.0 | 510 |
| /24 (C) | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| /31 | 255.255.255.254 | *2 |
| /32 | 255.255.255.255 | 1 |
| VLSM Bit | Value |
|---|---|
| 1 | 128 |
| 2 | 192 |
| 3 | 224 |
| 4 | 240 |
| 5 | 248 |
| 6 | 252 |
| 7 | 254 |
| 8 | 255 |
| Classful IP Ranges | ||||
|---|---|---|---|---|
| First Octet | Default Mask | Dotted Decimel | # of Networks | |
| A | 1-126 | /8 | 255.0.0.0 | 126 |
| B | 128-191 | /16 | 255.255.0.0 | 16,384 |
| C | 192-223 | /24 | 255.255.255.0 | 2,097,152 |
| D | 224-239 | multicast communication | ||
| E | 240-255 | experimental/reserved | ||
| Reserved IP Ranges | |
|---|---|
| 0.0.0.0/8 | "This" Network |
| 127.0.0.1/8 | Home/Loopback |
| 169.254.0.0/16 | Link-local address (APIPA) |
| 224.0.0.0/4 | IP Multicast |
| 255.255.255.255 | Broadcast "This" Network |
| Internal IP Ranges (Private) | ||||
|---|---|---|---|---|
| Class A | 10.0.0.0/8 | - | 10.255.255.255 | one block |
| Class B | 172.16.0.0/12 | - | 172.31.255.255 | 16 blocks (contiguous) |
| Class C | 192.168.0.0/16 | - | 192.168.255.255 | 256 Blocks (contiguous) |
*Special (Point-to-Point ONLY) rfc3021
Subnetting Attributes
| Attr | Explain | Formula |
|---|---|---|
| Network ID | First IP address in each Network (defines the network) | |
| Broadcast IP | Last IP in each Network | |
| First usable IP | first IP address after network ID | |
| Last usable IP | broadcast IP -1 | |
| # of Subnets/Networks | number of networks, in this particular sub network | 2^x (where x is the number of borrowed bits) |
| # of Usable Hosts/IPs | Number of usable IP addresses(Hosts) in each network | 2^y - 2 (where y is the number of bits remaining for the host portion) |
| Next Network | next IP after the broadcast IP |
Subnetting CHART/cheatSheet
| CIDR | Mask | Magic# | SubNets | |||
|---|---|---|---|---|---|---|
| /1 | /9 | /17 | /25 | 128 | 128 | 2 |
| /2 | /10 | /18 | /26 | 192 | 64 | 4 |
| /3 | /11 | /19 | /27 | 224 | 32 | 8 |
| /4 | /12 | /20 | /28 | 240 | 16 | 16 |
| /5 | /13 | /21 | /29 | 248 | 8 | 32 |
| /6 | /14 | /22 | /30 | 252 | 4 | 64 |
| /7 | /15 | /23 | /31 | 254 | 2 | 128 |
| /8 | /16 | /24 | /32 | 255 | 1 | 256 |
Multiples Chart
| Network ID | Values |
|---|---|
| 128 | 0-128, 129-255 |
| 64 | 0-63, 64-127, 128-191, 192-255 |
| 32 | 0-32,64,96,128,160,192,224 |
| 16 | 0-16,32,48,64,80,96,112,128,144,160,176,192,208,224,240 |
| 8 | 0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168,176,184,192,200,208,216,224,232,240,248 |
| 4 | 0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,132,136,140,144,148,152,156,160,164,168,172,176,180,184,188,192,196,200,204,208,212,216,220,224,248,252 |
x2 Multiples
| 2^1 | 2^2 | 2^3 | 2^4 | 2^5 | 2^6 | 2^7 | 2^8 | 2^9 | 2^10 |
|---|---|---|---|---|---|---|---|---|---|
| 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 |
| 2^11 | 2^12 | 2^13 | 2^14 | 2^15 | 2^16 | 2^17 | 2^18 | 2^19 | 2^20 |
| 2048 | 4096 | 8192 | 16384 | 32768 | 65536 | 131072 | 262144 | 524288 | 1048576 |