172.221.21.128/28
PublicClass B — /28 prefix — 14 usable hosts
Network address — the base address of the block (172.221.21.128). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 172.221.21.143 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 | 172.221.21.128/28 |
| Network Address | 172.221.21.128 |
| Broadcast Address | 172.221.21.143 |
| 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 | 172.221.21.129 |
| Last Usable IP | 172.221.21.142 |
| Network (Hex) | 0xACDD1580 |
| Broadcast (Hex) | 0xACDD158F |
| 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 172.221.21.128/28 into 2 equal /29 subnets (6 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.221.21.128/29 | 172.221.21.128 | 172.221.21.129 | 172.221.21.134 | 172.221.21.135 | 6 |
| 2 | 172.221.21.136/29 | 172.221.21.136 | 172.221.21.137 | 172.221.21.142 | 172.221.21.143 | 6 |
Split 172.221.21.128/28 into 4 equal /30 subnets (2 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.221.21.128/30 | 172.221.21.128 | 172.221.21.129 | 172.221.21.130 | 172.221.21.131 | 2 |
| 2 | 172.221.21.132/30 | 172.221.21.132 | 172.221.21.133 | 172.221.21.134 | 172.221.21.135 | 2 |
| 3 | 172.221.21.136/30 | 172.221.21.136 | 172.221.21.137 | 172.221.21.138 | 172.221.21.139 | 2 |
| 4 | 172.221.21.140/30 | 172.221.21.140 | 172.221.21.141 | 172.221.21.142 | 172.221.21.143 | 2 |