The practice of dividing a network into two or more networks is called subnetting. We steal bits from the hosts to create more subnets.
Public IP range, Used with the public network ex. WAN; Recognized over the internet, assigned by IANA or service provider. globally unique, cost associated with public IP.
| CLASS | IP Address Range | Network Mask | Prefix | Number of Networks | Number of hosts |
|---|---|---|---|---|---|
| A | 1 to 126, Used for huge networks, like those deployed by Internet Service Providers (ISPs). | 255.0.0.0 | /8 | 125 | 16,777,241 |
| B | 128 to 191, Used for medium and large-sized networks in enterprises and organizations | 255.255.0.0 | /16 | 16,382 | 65,534 |
| C | 192 to 223, Used for small-sized networks. | 255.255.255.0 | /24 | 2,097,150 | 254 |
| D | 224 to 239, Used for multicasting applications | Multicast Addresses | |||
| E | 240 to 254, Reserved for experimental purposes only for R&D or Study. | R&D, Restricted/Experimental |
The above table is standard and good to remember but the actual range will look like below after excluding private IP range.
| CLASS A | 1.0.0.0 - 9.255.255.255 11.0.0.0 - 126.255.255.255 |
|---|---|
| CLASS B | 128.0.0.0 - 172.15.255.255 172.32.0.0 - 191.255.255.255 |
| CLASS C | 192.0.0.0 - 192.167.255.255 192.169.0.0 - 223.255.255.255 |
127.0.0.0 is reserved for loopback (localhost).
Private IP range, Used with the private network ex. LAN; Not recognized over the internet, assigned by LAN Admin. unique only in LAN segment. free of charge.
| CLASS A | 10.0.0.0 - 10.255.255.255, Used for private network, local LAN. |
|---|---|
| CLASS B | 172.16.0.0 - 172.31.255.255, Used for private network, local LAN. |
| CLASS C | 192.168.0.0 - 192.168.255.255, Used for private network, local LAN. |
Types of Subnetting
- Fixed Length Subnetting - All the subnets are of same size, same subnet mask, equal number of hosts. It is also called as classful subnetting.
- Variable Length Subnetting - All the subnets are not of same size, do not have same subnet mask, no equal number of hosts. It is also called as classless subnetting
Types of addresses
- Network address - Network address represents the network.
- Broadcast address - Broadcast address represents all the hosts which belong to it.
Subnetting Table (Class A),
| NetBits | Network Mask | Subnets | Number of Hosts |
|---|---|---|---|
| /8 | 255.0.0.0 | 0 | 16,777,214 |
| /9 | 255.128.0.0 | 0 | 8,388,606 |
| /10 | 255.192.0.0 | 2 | 4,194,302 |
| /11 | 255.224.0.0 | 6 | 2,097,150 |
| /12 | 255.240.0.0 | 14 | 1,048,574 |
| /13 | 255.248.0.0 | 30 | 524,286 |
| /14 | 255.252.0.0 | 62 | 262,142 |
| /15 | 255.254.0.0 | 126 | 131,070 |
| /16 | 255.255.0.0 | 254 | 65,534 |
| /17 | 255.255.128.0 | 510 | 32,766 |
| /18 | 255.255.192.0 | 1,022 | 16,382 |
| /19 | 255.255.224.0 | 2,046 | 8,190 |
| /20 | 255.255.240.0 | 4,094 | 4,094 |
| /21 | 255.255.248.0 | 8,190 | 2,046 |
| /22 | 255.255.252.0 | 16,382 | 1,022 |
| /23 | 255.255.254.0 | 32,766 | 510 |
| /24 | 255.255.255.0 | 65,534 | 254 |
| /25 | 255.255.255.128 | 131,070 | 126 |
| /26 | 255.255.255.192 | 262,142 | 62 |
| /27 | 255.255.255.224 | 524,286 | 30 |
| /28 | 255.255.255.240 | 1,048,574 | 14 |
| /29 | 255.255.255.248 | 2,097,150 | 6 |
| /30 | 255.255.255.252 | 4,194,302 | 2 |
Subnetting Table (Class B),
| NetBits | Network Mask | Subnets | Number of Hosts |
|---|---|---|---|
| /16 | 255.255.0.0 | 0 | 65,534 |
| /17 | 255.255.128.0 | 0 | 32,766 |
| /18 | 255.255.192.0 | 2 | 16,382 |
| /19 | 255.255.224.0 | 6 | 8,190 |
| /20 | 255.255.240.0 | 14 | 4,094 |
| /21 | 255.255.248.0 | 30 | 2,046 |
| /22 | 255.255.252.0 | 62 | 1,022 |
| /23 | 255.255.254.0 | 126 | 510 |
| /24 | 255.255.255.0 | 254 | 254 |
| /25 | 255.255.255.128 | 510 | 126 |
| /26 | 255.255.255.192 | 1,022 | 62 |
| /27 | 255.255.255.224 | 2,046 | 30 |
| /28 | 255.255.255.240 | 4,094 | 14 |
| /29 | 255.255.255.248 | 8,190 | 6 |
| /30 | 255.255.255.252 | 16,382 | 2 |
Subnetting Table (Class C),
| NetBits | Network Mask | Subnets | Number of Hosts |
|---|---|---|---|
| /24 | 255.255.255.0 | 0 | 254 |
| /25 | 255.255.255.128 | 0 | 126 |
| /26 | 255.255.255.192 | 2 | 62 |
| /27 | 255.255.255.224 | 6 | 30 |
| /28 | 255.255.255.240 | 14 | 14 |
| /29 | 255.255.255.248 | 30 | 6 |
| /30 | 255.255.255.252 | 62 | 2 |