18.81.128.0/18
PublicClass A — /18 prefix — 16,382 usable hosts
Network address — the base address of the block (18.81.128.0). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 18.81.191.255 are delivered to every device in the subnet. Also reserved — not assignable.
Usable hosts — the 16,382 addresses between those two that you can assign to servers, VMs, or interfaces.
Subnet mask — 255.255.192.0 is the dotted-decimal equivalent of /18. Older tools and Cisco configs use this format instead of CIDR slash notation.
Full Details
| CIDR Notation | 18.81.128.0/18 |
| Network Address | 18.81.128.0 |
| Broadcast Address | 18.81.191.255 |
| Subnet Mask | 255.255.192.0 |
| Wildcard Mask | 0.0.63.255 |
| Prefix Length | /18 |
| IP Address Class | Class A |
| Total IP Addresses | 16,384 |
| Usable Host Addresses | 16,382 |
| First Usable IP | 18.81.128.1 |
| Last Usable IP | 18.81.191.254 |
| Network (Hex) | 0x12518000 |
| Broadcast (Hex) | 0x1251BFFF |
| Address Type | Public / Globally Routable |
Binary Representation
The first 18 bits (1s in the mask) identify the network. The remaining 14 bits identify hosts within the network.
Split into Equal Subnets
Split 18.81.128.0/18 into 2 equal /19 subnets (8,190 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 18.81.128.0/19 | 18.81.128.0 | 18.81.128.1 | 18.81.159.254 | 18.81.159.255 | 8,190 |
| 2 | 18.81.160.0/19 | 18.81.160.0 | 18.81.160.1 | 18.81.191.254 | 18.81.191.255 | 8,190 |
Split 18.81.128.0/18 into 4 equal /20 subnets (4,094 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 18.81.128.0/20 | 18.81.128.0 | 18.81.128.1 | 18.81.143.254 | 18.81.143.255 | 4,094 |
| 2 | 18.81.144.0/20 | 18.81.144.0 | 18.81.144.1 | 18.81.159.254 | 18.81.159.255 | 4,094 |
| 3 | 18.81.160.0/20 | 18.81.160.0 | 18.81.160.1 | 18.81.175.254 | 18.81.175.255 | 4,094 |
| 4 | 18.81.176.0/20 | 18.81.176.0 | 18.81.176.1 | 18.81.191.254 | 18.81.191.255 | 4,094 |
Split 18.81.128.0/18 into 8 equal /21 subnets (2,046 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 18.81.128.0/21 | 18.81.128.0 | 18.81.128.1 | 18.81.135.254 | 18.81.135.255 | 2,046 |
| 2 | 18.81.136.0/21 | 18.81.136.0 | 18.81.136.1 | 18.81.143.254 | 18.81.143.255 | 2,046 |
| 3 | 18.81.144.0/21 | 18.81.144.0 | 18.81.144.1 | 18.81.151.254 | 18.81.151.255 | 2,046 |
| 4 | 18.81.152.0/21 | 18.81.152.0 | 18.81.152.1 | 18.81.159.254 | 18.81.159.255 | 2,046 |
| 5 | 18.81.160.0/21 | 18.81.160.0 | 18.81.160.1 | 18.81.167.254 | 18.81.167.255 | 2,046 |
| 6 | 18.81.168.0/21 | 18.81.168.0 | 18.81.168.1 | 18.81.175.254 | 18.81.175.255 | 2,046 |
| 7 | 18.81.176.0/21 | 18.81.176.0 | 18.81.176.1 | 18.81.183.254 | 18.81.183.255 | 2,046 |
| 8 | 18.81.184.0/21 | 18.81.184.0 | 18.81.184.1 | 18.81.191.254 | 18.81.191.255 | 2,046 |
Split 18.81.128.0/18 into 16 equal /22 subnets (1,022 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 18.81.128.0/22 | 18.81.128.0 | 18.81.128.1 | 18.81.131.254 | 18.81.131.255 | 1,022 |
| 2 | 18.81.132.0/22 | 18.81.132.0 | 18.81.132.1 | 18.81.135.254 | 18.81.135.255 | 1,022 |
| 3 | 18.81.136.0/22 | 18.81.136.0 | 18.81.136.1 | 18.81.139.254 | 18.81.139.255 | 1,022 |
| 4 | 18.81.140.0/22 | 18.81.140.0 | 18.81.140.1 | 18.81.143.254 | 18.81.143.255 | 1,022 |
| 5 | 18.81.144.0/22 | 18.81.144.0 | 18.81.144.1 | 18.81.147.254 | 18.81.147.255 | 1,022 |
| 6 | 18.81.148.0/22 | 18.81.148.0 | 18.81.148.1 | 18.81.151.254 | 18.81.151.255 | 1,022 |
| 7 | 18.81.152.0/22 | 18.81.152.0 | 18.81.152.1 | 18.81.155.254 | 18.81.155.255 | 1,022 |
| 8 | 18.81.156.0/22 | 18.81.156.0 | 18.81.156.1 | 18.81.159.254 | 18.81.159.255 | 1,022 |
| 9 | 18.81.160.0/22 | 18.81.160.0 | 18.81.160.1 | 18.81.163.254 | 18.81.163.255 | 1,022 |
| 10 | 18.81.164.0/22 | 18.81.164.0 | 18.81.164.1 | 18.81.167.254 | 18.81.167.255 | 1,022 |
| 11 | 18.81.168.0/22 | 18.81.168.0 | 18.81.168.1 | 18.81.171.254 | 18.81.171.255 | 1,022 |
| 12 | 18.81.172.0/22 | 18.81.172.0 | 18.81.172.1 | 18.81.175.254 | 18.81.175.255 | 1,022 |
| 13 | 18.81.176.0/22 | 18.81.176.0 | 18.81.176.1 | 18.81.179.254 | 18.81.179.255 | 1,022 |
| 14 | 18.81.180.0/22 | 18.81.180.0 | 18.81.180.1 | 18.81.183.254 | 18.81.183.255 | 1,022 |
| 15 | 18.81.184.0/22 | 18.81.184.0 | 18.81.184.1 | 18.81.187.254 | 18.81.187.255 | 1,022 |
| 16 | 18.81.188.0/22 | 18.81.188.0 | 18.81.188.1 | 18.81.191.254 | 18.81.191.255 | 1,022 |