251.0.0.0/8
PublicClass E (Reserved) — /8 prefix — 16,777,214 usable hosts
Network address — the base address of the block (251.0.0.0). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 251.255.255.255 are delivered to every device in the subnet. Also reserved — not assignable.
Usable hosts — the 16,777,214 addresses between those two that you can assign to servers, VMs, or interfaces.
Subnet mask — 255.0.0.0 is the dotted-decimal equivalent of /8. Older tools and Cisco configs use this format instead of CIDR slash notation.
Full Details
| CIDR Notation | 251.0.0.0/8 |
| Network Address | 251.0.0.0 |
| Broadcast Address | 251.255.255.255 |
| Subnet Mask | 255.0.0.0 |
| Wildcard Mask | 0.255.255.255 |
| Prefix Length | /8 |
| IP Address Class | Class E (Reserved) |
| Total IP Addresses | 16,777,216 |
| Usable Host Addresses | 16,777,214 |
| First Usable IP | 251.0.0.1 |
| Last Usable IP | 251.255.255.254 |
| Network (Hex) | 0xFB000000 |
| Broadcast (Hex) | 0xFBFFFFFF |
| Address Type | Public / Globally Routable |
Binary Representation
The first 8 bits (1s in the mask) identify the network. The remaining 24 bits identify hosts within the network.
Split into Equal Subnets
Split 251.0.0.0/8 into 2 equal /9 subnets (8,388,606 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 251.0.0.0/9 | 251.0.0.0 | 251.0.0.1 | 251.127.255.254 | 251.127.255.255 | 8,388,606 |
| 2 | 251.128.0.0/9 | 251.128.0.0 | 251.128.0.1 | 251.255.255.254 | 251.255.255.255 | 8,388,606 |
Split 251.0.0.0/8 into 4 equal /10 subnets (4,194,302 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 251.0.0.0/10 | 251.0.0.0 | 251.0.0.1 | 251.63.255.254 | 251.63.255.255 | 4,194,302 |
| 2 | 251.64.0.0/10 | 251.64.0.0 | 251.64.0.1 | 251.127.255.254 | 251.127.255.255 | 4,194,302 |
| 3 | 251.128.0.0/10 | 251.128.0.0 | 251.128.0.1 | 251.191.255.254 | 251.191.255.255 | 4,194,302 |
| 4 | 251.192.0.0/10 | 251.192.0.0 | 251.192.0.1 | 251.255.255.254 | 251.255.255.255 | 4,194,302 |
Split 251.0.0.0/8 into 8 equal /11 subnets (2,097,150 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 251.0.0.0/11 | 251.0.0.0 | 251.0.0.1 | 251.31.255.254 | 251.31.255.255 | 2,097,150 |
| 2 | 251.32.0.0/11 | 251.32.0.0 | 251.32.0.1 | 251.63.255.254 | 251.63.255.255 | 2,097,150 |
| 3 | 251.64.0.0/11 | 251.64.0.0 | 251.64.0.1 | 251.95.255.254 | 251.95.255.255 | 2,097,150 |
| 4 | 251.96.0.0/11 | 251.96.0.0 | 251.96.0.1 | 251.127.255.254 | 251.127.255.255 | 2,097,150 |
| 5 | 251.128.0.0/11 | 251.128.0.0 | 251.128.0.1 | 251.159.255.254 | 251.159.255.255 | 2,097,150 |
| 6 | 251.160.0.0/11 | 251.160.0.0 | 251.160.0.1 | 251.191.255.254 | 251.191.255.255 | 2,097,150 |
| 7 | 251.192.0.0/11 | 251.192.0.0 | 251.192.0.1 | 251.223.255.254 | 251.223.255.255 | 2,097,150 |
| 8 | 251.224.0.0/11 | 251.224.0.0 | 251.224.0.1 | 251.255.255.254 | 251.255.255.255 | 2,097,150 |
Split 251.0.0.0/8 into 16 equal /12 subnets (1,048,574 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 251.0.0.0/12 | 251.0.0.0 | 251.0.0.1 | 251.15.255.254 | 251.15.255.255 | 1,048,574 |
| 2 | 251.16.0.0/12 | 251.16.0.0 | 251.16.0.1 | 251.31.255.254 | 251.31.255.255 | 1,048,574 |
| 3 | 251.32.0.0/12 | 251.32.0.0 | 251.32.0.1 | 251.47.255.254 | 251.47.255.255 | 1,048,574 |
| 4 | 251.48.0.0/12 | 251.48.0.0 | 251.48.0.1 | 251.63.255.254 | 251.63.255.255 | 1,048,574 |
| 5 | 251.64.0.0/12 | 251.64.0.0 | 251.64.0.1 | 251.79.255.254 | 251.79.255.255 | 1,048,574 |
| 6 | 251.80.0.0/12 | 251.80.0.0 | 251.80.0.1 | 251.95.255.254 | 251.95.255.255 | 1,048,574 |
| 7 | 251.96.0.0/12 | 251.96.0.0 | 251.96.0.1 | 251.111.255.254 | 251.111.255.255 | 1,048,574 |
| 8 | 251.112.0.0/12 | 251.112.0.0 | 251.112.0.1 | 251.127.255.254 | 251.127.255.255 | 1,048,574 |
| 9 | 251.128.0.0/12 | 251.128.0.0 | 251.128.0.1 | 251.143.255.254 | 251.143.255.255 | 1,048,574 |
| 10 | 251.144.0.0/12 | 251.144.0.0 | 251.144.0.1 | 251.159.255.254 | 251.159.255.255 | 1,048,574 |
| 11 | 251.160.0.0/12 | 251.160.0.0 | 251.160.0.1 | 251.175.255.254 | 251.175.255.255 | 1,048,574 |
| 12 | 251.176.0.0/12 | 251.176.0.0 | 251.176.0.1 | 251.191.255.254 | 251.191.255.255 | 1,048,574 |
| 13 | 251.192.0.0/12 | 251.192.0.0 | 251.192.0.1 | 251.207.255.254 | 251.207.255.255 | 1,048,574 |
| 14 | 251.208.0.0/12 | 251.208.0.0 | 251.208.0.1 | 251.223.255.254 | 251.223.255.255 | 1,048,574 |
| 15 | 251.224.0.0/12 | 251.224.0.0 | 251.224.0.1 | 251.239.255.254 | 251.239.255.255 | 1,048,574 |
| 16 | 251.240.0.0/12 | 251.240.0.0 | 251.240.0.1 | 251.255.255.254 | 251.255.255.255 | 1,048,574 |