Subnetting is the process of dividing one network into smaller networks. Collectively, the smaller networks are referred to as subnetworks (or subnets), and the singular subdivision is a subnetwork (more commonly referred to as a subnet). Every single computer that is connected to a subnet shares an identical portion of the IP address. This shared information is known as a routing prefix, and in IPV4 (Internet Protocol Version 4), the routing prefix is called a subnet mask. The subnet mask is a "quad-dotted decimal representation".
This IPv4 Subnet Chart can assist you in looking up how a network is broken up into subnets.
Class address ranges:
- Class A = 1.0.0.0 to 126.0.0.0
- Class B = 128.0.0.0 to 191.255.0.0
- Class C = 192.0.1.0 to 223.255.255.0
Reserved address ranges for private (non-routed) use:
- 10.0.0.0 -> 10.255.255.255
- 172.16.0.0 -> 172.31.255.255
- 192.168.0.0 -> 192.168.255.255
Other reserved addresses:
- 127.0.0.0 is reserved for loopback and IPC on the local host
- 224.0.0.0 -> 239.255.255.255 is reserved for multicast addresses
Chart notes:
- Number of Subnets - "( )" Refers to the number of effective subnets, since the use of subnet numbers of all 0s or all 1s is highly frowned upon and RFC non-compliant.
- Number of Hosts - Refers to the number of effective hosts, excluding the network and broadcast address.
Class A
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/8 | 255.0.0.0 | 0 | 16777214 |
/9 | 255.128.0.0 | 2 (0) | 8388606 |
/10 | 255.192.0.0 | 4 (2) | 4194302 |
/11 | 255.224.0.0 | 8 (6) | 2097150 |
/12 | 255.240.0.0 | 16 (14) | 1048574 |
/13 | 255.248.0.0 | 32 (30) | 524286 |
/14 | 255.252.0.0 | 64 (62) | 262142 |
/15 | 255.254.0.0 | 128 (126) | 131070 |
/16 | 255.255.0.0 | 256 (254) | 65534 |
/17 | 255.255.128.0 | 512 (510) | 32766 |
/18 | 255.255.192.0 | 1024 (1022) | 16382 |
/19 | 255.255.224.0 | 2048 (2046) | 8190 |
/20 | 255.255.240.0 | 4096 (4094) | 4094 |
/21 | 255.255.248.0 | 8192 (8190) | 2046 |
/22 | 255.255.252.0 | 16384 (16382) | 1022 |
/23 | 255.255.254.0 | 32768 (32766) | 510 |
/24 | 255.255.255.0 | 65536 (65534) | 254 |
/25 | 255.255.255.128 | 131072 (131070) | 126 |
/26 | 255.255.255.192 | 262144 (262142) | 62 |
/27 | 255.255.255.224 | 524288 (524286) | 30 |
/28 | 255.255.255.240 | 1048576 (1048574) | 14 |
/29 | 255.255.255.248 | 2097152 (2097150) | 6 |
/30 | 255.255.255.252 | 4194304 (4194302) | 2 |
Class B
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/16 | 255.255.0.0 | 0 | 65534 |
/17 | 255.255.128.0 | 2 (0) | 32766 |
/18 | 255.255.192.0 | 4 (2) | 16382 |
/19 | 255.255.224.0 | 8 (6) | 8190 |
/20 | 255.255.240.0 | 16 (14) | 4094 |
/21 | 255.255.248.0 | 32 (30) | 2046 |
/22 | 255.255.252.0 | 64 (62) | 1022 |
/23 | 255.255.254.0 | 128 (126) | 510 |
/24 | 255.255.255.0 | 256 (254) | 254 |
/25 | 255.255.255.128 | 512 (510) | 126 |
/26 | 255.255.255.192 | 1024 (1022) | 62 |
/27 | 255.255.255.224 | 2048 (2046) | 30 |
/28 | 255.255.255.240 | 4096 (4094) | 14 |
/29 | 255.255.255.248 | 8192 (8190) | 6 |
/30 | 255.255.255.252 | 16384 (16382) | 2 |
Class C
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/24 | 255.255.255.0 | 0 | 254 |
/25 | 255.255.255.128 | 2 (0) | 126 |
/26 | 255.255.255.192 | 4 (2) | 62 |
/27 | 255.255.255.224 | 8 (6) | 30 |
/28 | 255.255.255.240 | 16 (14) | 14 |
/29 | 255.255.255.248 | 32 (30) | 6 |
/30 | 255.255.255.252 | 64 (62) | 2 |
Class D
CIDR Block | Supernet Mask | Number of Class C Addresses | Number of Hosts |
/14 | 255.252.0.0 | 1024 | 262144 |
/15 | 255.254.0.0 | 512 | 131072 |
/16 | 255.255.0.0 | 256 | 65536 |
/17 | 255.255.128.0 | 128 | 32768 |
/18 | 255.255.192.0 | 64 | 16384 |
/19 | 255.255.224.0 | 32 | 8192 |
/20 | 255.255.240.0 | 16 | 4096 |
/21 | 255.255.248.0 | 8 | 2048 |
/22 | 255.255.252.0 | 4 | 1024 |
/23 | 255.255.254.0 | 2 | 512 |
What is the maximum number of usable hosts with a class B network address?
Class B Networks (/16 Prefixes)
This network is a 16-bit network prefix; its highest bit order is set to 1-0. It is a 14-bit network number with a 16-bit host number. This class defines 16,384 (2 14 ) /16 networks, and supports a maximum of 65,534 (2 16 -2) hosts per network.
What is the maximum number of host IP addresses?
so 2^11 = 2048. Out of this addresses the first and last address correspond to network and broadcast address which cannot be used for host. i.e 2048-2 = 2046 are the maximum number of host the given range of IP address can have.
What is the size of host in Class B IP address?
A class B network number uses 16 bits for the network number and 16 bits for host numbers.