100.121.138.80/28
PublicClass A — /28 prefix — 14 usable hosts
Network address — the base address of the block (100.121.138.80). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 100.121.138.95 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 | 100.121.138.80/28 |
| Network Address | 100.121.138.80 |
| Broadcast Address | 100.121.138.95 |
| 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 | 100.121.138.81 |
| Last Usable IP | 100.121.138.94 |
| Network (Hex) | 0x64798A50 |
| Broadcast (Hex) | 0x64798A5F |
| 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 100.121.138.80/28 into 2 equal /29 subnets (6 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 100.121.138.80/29 | 100.121.138.80 | 100.121.138.81 | 100.121.138.86 | 100.121.138.87 | 6 |
| 2 | 100.121.138.88/29 | 100.121.138.88 | 100.121.138.89 | 100.121.138.94 | 100.121.138.95 | 6 |
Split 100.121.138.80/28 into 4 equal /30 subnets (2 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 100.121.138.80/30 | 100.121.138.80 | 100.121.138.81 | 100.121.138.82 | 100.121.138.83 | 2 |
| 2 | 100.121.138.84/30 | 100.121.138.84 | 100.121.138.85 | 100.121.138.86 | 100.121.138.87 | 2 |
| 3 | 100.121.138.88/30 | 100.121.138.88 | 100.121.138.89 | 100.121.138.90 | 100.121.138.91 | 2 |
| 4 | 100.121.138.92/30 | 100.121.138.92 | 100.121.138.93 | 100.121.138.94 | 100.121.138.95 | 2 |