/4 Subnet Mask
A /4 prefix means the subnet mask is 240.0.0.0. It has 28 host bits, giving 268,435,456 total addresses and 268,435,454 usable hosts.
/4 at a glance
| Property | Value |
|---|---|
| CIDR prefix | /4 |
| Subnet mask | 240.0.0.0 |
| Wildcard mask | 15.255.255.255 |
| Total addresses | 268,435,456 |
| Usable hosts | 268,435,454 |
| Host bits | 28 |
How it is calculated
A /4 sets the first 4 bits to 1 (network) and the remaining 28 bits to 0 (host). Usable hosts = 228 − 2 = 268,435,454.
The wildcard mask 15.255.255.255 is the inverse — used in Cisco ACLs and OSPF network statements.
Frequently asked questions
What is a /4 subnet mask?
A /4 equals 240.0.0.0 in dotted decimal (wildcard 15.255.255.255). It provides 268,435,456 total addresses and 268,435,454 usable hosts.
How many hosts are in a /4?
A /4 has 28 host bits, so it supports 268,435,454 usable hosts.
What is the wildcard mask for /4?
The wildcard (inverse) mask for /4 is 15.255.255.255, used in Cisco ACLs and OSPF statements.
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