121.23.9.16/28
PublicClass A — /28 prefix — 14 usable hosts
Network address — the base address of the block (121.23.9.16). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 121.23.9.31 are delivered to every device in the subnet. Also reserved — not assignable.
Usable hosts — the 14 addresses between those two that you can assign to servers, VMs, or interfaces.
Subnet mask — 255.255.255.240 is the dotted-decimal equivalent of /28. Older tools and Cisco configs use this format instead of CIDR slash notation.
Full Details
| CIDR Notation | 121.23.9.16/28 |
| Network Address | 121.23.9.16 |
| Broadcast Address | 121.23.9.31 |
| Subnet Mask | 255.255.255.240 |
| Wildcard Mask | 0.0.0.15 |
| Prefix Length | /28 |
| IP Address Class | Class A |
| Total IP Addresses | 16 |
| Usable Host Addresses | 14 |
| First Usable IP | 121.23.9.17 |
| Last Usable IP | 121.23.9.30 |
| Network (Hex) | 0x79170910 |
| Broadcast (Hex) | 0x7917091F |
| Address Type | Public / Globally Routable |
Binary Representation
The first 28 bits (1s in the mask) identify the network. The remaining 4 bits identify hosts within the network.
Split into Equal Subnets
Split 121.23.9.16/28 into 2 equal /29 subnets (6 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 121.23.9.16/29 | 121.23.9.16 | 121.23.9.17 | 121.23.9.22 | 121.23.9.23 | 6 |
| 2 | 121.23.9.24/29 | 121.23.9.24 | 121.23.9.25 | 121.23.9.30 | 121.23.9.31 | 6 |
Split 121.23.9.16/28 into 4 equal /30 subnets (2 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 121.23.9.16/30 | 121.23.9.16 | 121.23.9.17 | 121.23.9.18 | 121.23.9.19 | 2 |
| 2 | 121.23.9.20/30 | 121.23.9.20 | 121.23.9.21 | 121.23.9.22 | 121.23.9.23 | 2 |
| 3 | 121.23.9.24/30 | 121.23.9.24 | 121.23.9.25 | 121.23.9.26 | 121.23.9.27 | 2 |
| 4 | 121.23.9.28/30 | 121.23.9.28 | 121.23.9.29 | 121.23.9.30 | 121.23.9.31 | 2 |