255.217.21.208/28
PublicClass E (Reserved) — /28 prefix — 14 usable hosts
Network address — the base address of the block (255.217.21.208). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 255.217.21.223 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 | 255.217.21.208/28 |
| Network Address | 255.217.21.208 |
| Broadcast Address | 255.217.21.223 |
| Subnet Mask | 255.255.255.240 |
| Wildcard Mask | 0.0.0.15 |
| Prefix Length | /28 |
| IP Address Class | Class E (Reserved) |
| Total IP Addresses | 16 |
| Usable Host Addresses | 14 |
| First Usable IP | 255.217.21.209 |
| Last Usable IP | 255.217.21.222 |
| Network (Hex) | 0xFFD915D0 |
| Broadcast (Hex) | 0xFFD915DF |
| 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 255.217.21.208/28 into 2 equal /29 subnets (6 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 255.217.21.208/29 | 255.217.21.208 | 255.217.21.209 | 255.217.21.214 | 255.217.21.215 | 6 |
| 2 | 255.217.21.216/29 | 255.217.21.216 | 255.217.21.217 | 255.217.21.222 | 255.217.21.223 | 6 |
Split 255.217.21.208/28 into 4 equal /30 subnets (2 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 255.217.21.208/30 | 255.217.21.208 | 255.217.21.209 | 255.217.21.210 | 255.217.21.211 | 2 |
| 2 | 255.217.21.212/30 | 255.217.21.212 | 255.217.21.213 | 255.217.21.214 | 255.217.21.215 | 2 |
| 3 | 255.217.21.216/30 | 255.217.21.216 | 255.217.21.217 | 255.217.21.218 | 255.217.21.219 | 2 |
| 4 | 255.217.21.220/30 | 255.217.21.220 | 255.217.21.221 | 255.217.21.222 | 255.217.21.223 | 2 |