What is a /18 subnet?
16,382 usable hosts out of 16,384 addresses, behind netmask 255.255.192.0.
| Prefix | /18 |
|---|---|
| Netmask | 255.255.192.0 |
| Wildcard | 0.0.63.255 |
| Total addresses | 16,384 |
| Usable hosts | 16,382 |
| Example block | 10.0.0.0/18 |
| Usable host range | 10.0.0.1 – 10.0.63.254 |
| Broadcast | 10.0.63.255 |
A /18 fixes the first 18 bits of the address as the network and leaves 14 for hosts — 16,384 addresses in all.
Of those, 16,382 can be given to a machine: the first address names the network itself, and the last is the broadcast address.
This is the usual size for a VPC or a site: room for tens of thousands of addresses, divided into smaller subnets per zone or per service.
It is 64 times the size of a /24.
Other subnet sizes
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