172.178.21.64/28
PublicClass B — /28 prefix — 14 usable hosts
Network address — the base address of the block (172.178.21.64). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 172.178.21.79 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 | 172.178.21.64/28 |
| Network Address | 172.178.21.64 |
| Broadcast Address | 172.178.21.79 |
| Subnet Mask | 255.255.255.240 |
| Wildcard Mask | 0.0.0.15 |
| Prefix Length | /28 |
| IP Address Class | Class B |
| Total IP Addresses | 16 |
| Usable Host Addresses | 14 |
| First Usable IP | 172.178.21.65 |
| Last Usable IP | 172.178.21.78 |
| Network (Hex) | 0xACB21540 |
| Broadcast (Hex) | 0xACB2154F |
| 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 172.178.21.64/28 into 2 equal /29 subnets (6 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.178.21.64/29 | 172.178.21.64 | 172.178.21.65 | 172.178.21.70 | 172.178.21.71 | 6 |
| 2 | 172.178.21.72/29 | 172.178.21.72 | 172.178.21.73 | 172.178.21.78 | 172.178.21.79 | 6 |
Split 172.178.21.64/28 into 4 equal /30 subnets (2 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.178.21.64/30 | 172.178.21.64 | 172.178.21.65 | 172.178.21.66 | 172.178.21.67 | 2 |
| 2 | 172.178.21.68/30 | 172.178.21.68 | 172.178.21.69 | 172.178.21.70 | 172.178.21.71 | 2 |
| 3 | 172.178.21.72/30 | 172.178.21.72 | 172.178.21.73 | 172.178.21.74 | 172.178.21.75 | 2 |
| 4 | 172.178.21.76/30 | 172.178.21.76 | 172.178.21.77 | 172.178.21.78 | 172.178.21.79 | 2 |