What is a /20 subnet?
4,094 usable hosts out of 4,096 addresses, behind netmask 255.255.240.0.
| Prefix | /20 |
|---|---|
| Netmask | 255.255.240.0 |
| Wildcard | 0.0.15.255 |
| Total addresses | 4,096 |
| Usable hosts | 4,094 |
| Example block | 10.0.0.0/20 |
| Usable host range | 10.0.0.1 – 10.0.15.254 |
| Broadcast | 10.0.15.255 |
A /20 fixes the first 20 bits of the address as the network and leaves 12 for hosts — 4,096 addresses in all.
Of those, 4,094 can be given to a machine: the first address names the network itself, and the last is the broadcast address.
A comfortable size for a large subnet or a small site — more than a single /24, without committing a whole /16.
It is 16 times the size of a /24.
Other subnet sizes
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