What is a /30 subnet?
2 usable hosts out of 4 addresses, behind netmask 255.255.255.252.
| Prefix | /30 |
|---|---|
| Netmask | 255.255.255.252 |
| Wildcard | 0.0.0.3 |
| Total addresses | 4 |
| Usable hosts | 2 |
| Example block | 10.0.0.0/30 |
| Usable host range | 10.0.0.1 – 10.0.0.2 |
| Broadcast | 10.0.0.3 |
A /30 fixes the first 30 bits of the address as the network and leaves 2 for hosts — 4 addresses in all.
Of those, 2 can be given to a machine: the first address names the network itself, and the last is the broadcast address.
Small enough to count on your fingers: a handful of servers, a load-balancer pool, or the linking network between two devices.
64 of them fit inside a /24.
Other subnet sizes
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