/21 Subnet Mask Reference (255.255.248.0)
Custom CIDR block with 2,048 total IPv4 addresses (2,046 usable host IPs) for VLSM allocation.
| CIDR Prefix | /21 |
|---|---|
| Subnet Mask | 255.255.248.0 |
| Wildcard Mask (Cisco / ACL) | 0.0.7.255 |
| Total IPv4 Addresses | 2,048 |
| Usable Host IPs | 2,046 |
| Binary Subnet Mask | 11111111.11111111.11111000.00000000 |
| Example Block (10.0.0.0/21) | 10.0.0.0 – 10.0.7.255 |
| Example Usable Hosts | 10.0.0.1 – 10.0.7.254 |
Need to compute custom IP ranges? Try the Interactive Subnet Calculator or VLSM Splitter.