18.237.16.0/21
PublicClass A — /21 prefix — 2,046 usable hosts
Network address — the base address of the block (18.237.16.0). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 18.237.23.255 are delivered to every device in the subnet. Also reserved — not assignable.
Usable hosts — the 2,046 addresses between those two that you can assign to servers, VMs, or interfaces.
Subnet mask — 255.255.248.0 is the dotted-decimal equivalent of /21. Older tools and Cisco configs use this format instead of CIDR slash notation.
Full Details
| CIDR Notation | 18.237.16.0/21 |
| Network Address | 18.237.16.0 |
| Broadcast Address | 18.237.23.255 |
| Subnet Mask | 255.255.248.0 |
| Wildcard Mask | 0.0.7.255 |
| Prefix Length | /21 |
| IP Address Class | Class A |
| Total IP Addresses | 2,048 |
| Usable Host Addresses | 2,046 |
| First Usable IP | 18.237.16.1 |
| Last Usable IP | 18.237.23.254 |
| Network (Hex) | 0x12ED1000 |
| Broadcast (Hex) | 0x12ED17FF |
| Address Type | Public / Globally Routable |
Binary Representation
The first 21 bits (1s in the mask) identify the network. The remaining 11 bits identify hosts within the network.
Subnet Breakdown — splitting into /22
This /21 block can be divided into 2 /22 subnets.
| CIDR | Network | Broadcast | First Usable | Last Usable | Hosts |
|---|---|---|---|---|---|
| 18.237.16.0/22 | 18.237.16.0 | 18.237.19.255 | 18.237.16.1 | 18.237.19.254 | 1,022 |
| 18.237.20.0/22 | 18.237.20.0 | 18.237.23.255 | 18.237.20.1 | 18.237.23.254 | 1,022 |