The /19 prefix length is a prefix length with a subnet mask of 255.255.224.0 and a wildcard mask of 0.0.31.255.
The 19 subnet mask helps divide larger networks, like Class A and Class B networks, into smaller networks (subnetworks). Each of the subnetworks has a range of 8192 IP addresses. The first IP address in this range is the network ID, and the last IP address in this range is the broadcast IP address. Hence, there are 8190 usable IP addresses in a /19 subnet mask.
Subnetting with a /19 Subnet Mask (Example)
When subnetting a network with a /19 subnet mask, you have a total of 8192 IP addresses in each subnet. Let’s consider subnetting the network 192.168.0.0/16 (a class B network) with a /19 subnet mask:
- First Subnet:
- Network Address: 192.168.0.0
- Usable IP Range: 192.168.0.1 to 192.168.31.254
- Broadcast IP Address: 192.168.31.255
- Second Subnet:
- Network Address: 192.168.32.0
- Usable IP Range: 192.168.32.1 to 192.168.63.254
- Broadcast IP Address: 192.168.63.255
Here is a table of a network subnetted with /19 subnet mask;
| Subnet | Network Address | IP Range | Broadcast Address |
|---|---|---|---|
| 1 | 192.168.0.0 | 192.168.0.1 to 192.168.31.254 | 192.168.31.255 |
| 2 | 192.168.32.0 | 192.168.32.1 to 192.168.63.254 | 192.168.63.255 |
| 3 | 192.168.64.0 | 192.168.64.1 to 192.168.95.254 | 192.168.95.255 |
| 4 | 192.168.96.0 | 192.168.96.1 to 192.168.127.254 | 192.168.127.255 |
| 5 | 192.168.128.0 | 192.168.128.1 to 192.168.159.254 | 192.168.159.255 |
| 6 | 192.168.160.0 | 192.168.160.1 to 192.168.191.254 | 192.168.191.255 |
| 7 | 192.168.192.0 | 192.168.192.1 to 192.168.223.254 | 192.168.223.255 |
| 8 | 192.168.224.0 | 192.168.224.1 to 192.168.255.254 | 192.168.255.255 |
/19 Subnet Mask IP range
There is a range of 8192 IP addresses in a /19 subnet mask. The first IP address in this range is the network ID, and the last IP address is the broadcast IP address. Therefore, there are 8190 usable IP addresses in a /19 subnet mask.
/19 Subnet Mask Dotted Decimal Notation
The dotted decimal notation for a /19 subnet mask is 255.255.224.0. This value is gotten by setting the first 19 bits out of the 32 bits of the IPV4 address to 1s, setting the remaining 13 bits to 0s, and then converting from binary to decimal.
Subnetting Class B Network with /19 Subnet Mask
To subnet a class B network with a /19 subnet mask, we need to borrow 3 bits from the host bits, resulting in the binary representation 11111111.11111111.11100000.00000000. Remember, the original binary representation for the class B subnet mask is 11111111.11111111.00000000.00000000.
Number of Subnets
The formula for calculating the number of subnets remains 2^(number of borrowed bits). In this case, it yields 2^3 = 8 subnets.
However, adhering to RFC guidelines, two subnets are reserved for specific functions. Therefore, the usable number of subnets becomes 8 minus 2, resulting in 6 usable subnets.
Subnetting Class A Network with /19 Subnet Mask
To subnet a class A network with a /19 subnet mask which has a binary representation of 11111111.00000000.00000000.00000000, 11 bits are borrowed from the host bits and added to the network bits. This results in the binary representation 11111111.11111111.11100000.00000000.
Number of Subnets
The formula for calculating the number of subnets is 2^(number of borrowed bits). In this case, it results in 2^11 = 2048 subnets.
Observing RFC guidelines, two subnets are reserved for specific functions. Hence, the usable number of subnets becomes 2048 minus 2 = 2046 usable subnets.
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