172.30.216.0/21
Private (RFC 1918) RFC 1918Class B — /21 prefix — 2,046 usable hosts
Network address — the base address of the block (172.30.216.0). All devices in this subnet share this prefix. Cannot be assigned to a host.
Broadcast address — packets sent to 172.30.223.255 are delivered to every device in the subnet. Also reserved — not assignable.
Usable hosts — the 2,046 addresses between those two that you can assign to servers, VMs, or interfaces.
Subnet mask — 255.255.248.0 is the dotted-decimal equivalent of /21. Older tools and Cisco configs use this format instead of CIDR slash notation.
Full Details
| CIDR Notation | 172.30.216.0/21 |
| Network Address | 172.30.216.0 |
| Broadcast Address | 172.30.223.255 |
| Subnet Mask | 255.255.248.0 |
| Wildcard Mask | 0.0.7.255 |
| Prefix Length | /21 |
| IP Address Class | Class B |
| Total IP Addresses | 2,048 |
| Usable Host Addresses | 2,046 |
| First Usable IP | 172.30.216.1 |
| Last Usable IP | 172.30.223.254 |
| Network (Hex) | 0xAC1ED800 |
| Broadcast (Hex) | 0xAC1EDFFF |
| Governing RFC | RFC 1918 |
| Address Type | Private (RFC 1918) |
Binary Representation
The first 21 bits (1s in the mask) identify the network. The remaining 11 bits identify hosts within the network.
Split into Equal Subnets
Split 172.30.216.0/21 into 2 equal /22 subnets (1,022 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.30.216.0/22 | 172.30.216.0 | 172.30.216.1 | 172.30.219.254 | 172.30.219.255 | 1,022 |
| 2 | 172.30.220.0/22 | 172.30.220.0 | 172.30.220.1 | 172.30.223.254 | 172.30.223.255 | 1,022 |
Split 172.30.216.0/21 into 4 equal /23 subnets (510 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.30.216.0/23 | 172.30.216.0 | 172.30.216.1 | 172.30.217.254 | 172.30.217.255 | 510 |
| 2 | 172.30.218.0/23 | 172.30.218.0 | 172.30.218.1 | 172.30.219.254 | 172.30.219.255 | 510 |
| 3 | 172.30.220.0/23 | 172.30.220.0 | 172.30.220.1 | 172.30.221.254 | 172.30.221.255 | 510 |
| 4 | 172.30.222.0/23 | 172.30.222.0 | 172.30.222.1 | 172.30.223.254 | 172.30.223.255 | 510 |
Split 172.30.216.0/21 into 8 equal /24 subnets (254 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.30.216.0/24 | 172.30.216.0 | 172.30.216.1 | 172.30.216.254 | 172.30.216.255 | 254 |
| 2 | 172.30.217.0/24 | 172.30.217.0 | 172.30.217.1 | 172.30.217.254 | 172.30.217.255 | 254 |
| 3 | 172.30.218.0/24 | 172.30.218.0 | 172.30.218.1 | 172.30.218.254 | 172.30.218.255 | 254 |
| 4 | 172.30.219.0/24 | 172.30.219.0 | 172.30.219.1 | 172.30.219.254 | 172.30.219.255 | 254 |
| 5 | 172.30.220.0/24 | 172.30.220.0 | 172.30.220.1 | 172.30.220.254 | 172.30.220.255 | 254 |
| 6 | 172.30.221.0/24 | 172.30.221.0 | 172.30.221.1 | 172.30.221.254 | 172.30.221.255 | 254 |
| 7 | 172.30.222.0/24 | 172.30.222.0 | 172.30.222.1 | 172.30.222.254 | 172.30.222.255 | 254 |
| 8 | 172.30.223.0/24 | 172.30.223.0 | 172.30.223.1 | 172.30.223.254 | 172.30.223.255 | 254 |
Split 172.30.216.0/21 into 16 equal /25 subnets (126 usable hosts each).
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 172.30.216.0/25 | 172.30.216.0 | 172.30.216.1 | 172.30.216.126 | 172.30.216.127 | 126 |
| 2 | 172.30.216.128/25 | 172.30.216.128 | 172.30.216.129 | 172.30.216.254 | 172.30.216.255 | 126 |
| 3 | 172.30.217.0/25 | 172.30.217.0 | 172.30.217.1 | 172.30.217.126 | 172.30.217.127 | 126 |
| 4 | 172.30.217.128/25 | 172.30.217.128 | 172.30.217.129 | 172.30.217.254 | 172.30.217.255 | 126 |
| 5 | 172.30.218.0/25 | 172.30.218.0 | 172.30.218.1 | 172.30.218.126 | 172.30.218.127 | 126 |
| 6 | 172.30.218.128/25 | 172.30.218.128 | 172.30.218.129 | 172.30.218.254 | 172.30.218.255 | 126 |
| 7 | 172.30.219.0/25 | 172.30.219.0 | 172.30.219.1 | 172.30.219.126 | 172.30.219.127 | 126 |
| 8 | 172.30.219.128/25 | 172.30.219.128 | 172.30.219.129 | 172.30.219.254 | 172.30.219.255 | 126 |
| 9 | 172.30.220.0/25 | 172.30.220.0 | 172.30.220.1 | 172.30.220.126 | 172.30.220.127 | 126 |
| 10 | 172.30.220.128/25 | 172.30.220.128 | 172.30.220.129 | 172.30.220.254 | 172.30.220.255 | 126 |
| 11 | 172.30.221.0/25 | 172.30.221.0 | 172.30.221.1 | 172.30.221.126 | 172.30.221.127 | 126 |
| 12 | 172.30.221.128/25 | 172.30.221.128 | 172.30.221.129 | 172.30.221.254 | 172.30.221.255 | 126 |
| 13 | 172.30.222.0/25 | 172.30.222.0 | 172.30.222.1 | 172.30.222.126 | 172.30.222.127 | 126 |
| 14 | 172.30.222.128/25 | 172.30.222.128 | 172.30.222.129 | 172.30.222.254 | 172.30.222.255 | 126 |
| 15 | 172.30.223.0/25 | 172.30.223.0 | 172.30.223.1 | 172.30.223.126 | 172.30.223.127 | 126 |
| 16 | 172.30.223.128/25 | 172.30.223.128 | 172.30.223.129 | 172.30.223.254 | 172.30.223.255 | 126 |