What is a /27 subnet?
30 usable hosts out of 32 addresses, behind netmask 255.255.255.224.
| Prefix | /27 |
|---|---|
| Netmask | 255.255.255.224 |
| Wildcard | 0.0.0.31 |
| Total addresses | 32 |
| Usable hosts | 30 |
| Example block | 10.0.0.0/27 |
| Usable host range | 10.0.0.1 – 10.0.0.30 |
| Broadcast | 10.0.0.31 |
A /27 fixes the first 27 bits of the address as the network and leaves 5 for hosts — 32 addresses in all.
Of those, 30 can be given to a machine: the first address names the network itself, and the last is the broadcast address.
These are the everyday sizes. A /24 is one office, one VLAN or one cloud subnet; the smaller ones suit a rack, a service tier or a DMZ.
8 of them fit inside a /24.
Other subnet sizes
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