151.2.16.0/21
PublicClass B — /21 prefix — 2,046 usable hosts
Network address — the base address of the block (151.2.16.0). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 151.2.23.255 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 | 151.2.16.0/21 |
| Network Address | 151.2.16.0 |
| Broadcast Address | 151.2.23.255 |
| Subnet Mask | 255.255.248.0 |
| Wildcard Mask | 0.0.7.255 |
| Prefix Length | /21 |
| IP Address Class | Class B |
| Total IP Addresses | 2,048 |
| Usable Host Addresses | 2,046 |
| First Usable IP | 151.2.16.1 |
| Last Usable IP | 151.2.23.254 |
| Network (Hex) | 0x97021000 |
| Broadcast (Hex) | 0x970217FF |
| 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.
Split into Equal Subnets
Split 151.2.16.0/21 into 2 equal /22 subnets (1,022 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 151.2.16.0/22 | 151.2.16.0 | 151.2.16.1 | 151.2.19.254 | 151.2.19.255 | 1,022 |
| 2 | 151.2.20.0/22 | 151.2.20.0 | 151.2.20.1 | 151.2.23.254 | 151.2.23.255 | 1,022 |
Split 151.2.16.0/21 into 4 equal /23 subnets (510 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 151.2.16.0/23 | 151.2.16.0 | 151.2.16.1 | 151.2.17.254 | 151.2.17.255 | 510 |
| 2 | 151.2.18.0/23 | 151.2.18.0 | 151.2.18.1 | 151.2.19.254 | 151.2.19.255 | 510 |
| 3 | 151.2.20.0/23 | 151.2.20.0 | 151.2.20.1 | 151.2.21.254 | 151.2.21.255 | 510 |
| 4 | 151.2.22.0/23 | 151.2.22.0 | 151.2.22.1 | 151.2.23.254 | 151.2.23.255 | 510 |
Split 151.2.16.0/21 into 8 equal /24 subnets (254 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 151.2.16.0/24 | 151.2.16.0 | 151.2.16.1 | 151.2.16.254 | 151.2.16.255 | 254 |
| 2 | 151.2.17.0/24 | 151.2.17.0 | 151.2.17.1 | 151.2.17.254 | 151.2.17.255 | 254 |
| 3 | 151.2.18.0/24 | 151.2.18.0 | 151.2.18.1 | 151.2.18.254 | 151.2.18.255 | 254 |
| 4 | 151.2.19.0/24 | 151.2.19.0 | 151.2.19.1 | 151.2.19.254 | 151.2.19.255 | 254 |
| 5 | 151.2.20.0/24 | 151.2.20.0 | 151.2.20.1 | 151.2.20.254 | 151.2.20.255 | 254 |
| 6 | 151.2.21.0/24 | 151.2.21.0 | 151.2.21.1 | 151.2.21.254 | 151.2.21.255 | 254 |
| 7 | 151.2.22.0/24 | 151.2.22.0 | 151.2.22.1 | 151.2.22.254 | 151.2.22.255 | 254 |
| 8 | 151.2.23.0/24 | 151.2.23.0 | 151.2.23.1 | 151.2.23.254 | 151.2.23.255 | 254 |
Split 151.2.16.0/21 into 16 equal /25 subnets (126 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 151.2.16.0/25 | 151.2.16.0 | 151.2.16.1 | 151.2.16.126 | 151.2.16.127 | 126 |
| 2 | 151.2.16.128/25 | 151.2.16.128 | 151.2.16.129 | 151.2.16.254 | 151.2.16.255 | 126 |
| 3 | 151.2.17.0/25 | 151.2.17.0 | 151.2.17.1 | 151.2.17.126 | 151.2.17.127 | 126 |
| 4 | 151.2.17.128/25 | 151.2.17.128 | 151.2.17.129 | 151.2.17.254 | 151.2.17.255 | 126 |
| 5 | 151.2.18.0/25 | 151.2.18.0 | 151.2.18.1 | 151.2.18.126 | 151.2.18.127 | 126 |
| 6 | 151.2.18.128/25 | 151.2.18.128 | 151.2.18.129 | 151.2.18.254 | 151.2.18.255 | 126 |
| 7 | 151.2.19.0/25 | 151.2.19.0 | 151.2.19.1 | 151.2.19.126 | 151.2.19.127 | 126 |
| 8 | 151.2.19.128/25 | 151.2.19.128 | 151.2.19.129 | 151.2.19.254 | 151.2.19.255 | 126 |
| 9 | 151.2.20.0/25 | 151.2.20.0 | 151.2.20.1 | 151.2.20.126 | 151.2.20.127 | 126 |
| 10 | 151.2.20.128/25 | 151.2.20.128 | 151.2.20.129 | 151.2.20.254 | 151.2.20.255 | 126 |
| 11 | 151.2.21.0/25 | 151.2.21.0 | 151.2.21.1 | 151.2.21.126 | 151.2.21.127 | 126 |
| 12 | 151.2.21.128/25 | 151.2.21.128 | 151.2.21.129 | 151.2.21.254 | 151.2.21.255 | 126 |
| 13 | 151.2.22.0/25 | 151.2.22.0 | 151.2.22.1 | 151.2.22.126 | 151.2.22.127 | 126 |
| 14 | 151.2.22.128/25 | 151.2.22.128 | 151.2.22.129 | 151.2.22.254 | 151.2.22.255 | 126 |
| 15 | 151.2.23.0/25 | 151.2.23.0 | 151.2.23.1 | 151.2.23.126 | 151.2.23.127 | 126 |
| 16 | 151.2.23.128/25 | 151.2.23.128 | 151.2.23.129 | 151.2.23.254 | 151.2.23.255 | 126 |