/3 Subnet Mask
A /3 prefix means the subnet mask is 224.0.0.0. It has 29 host bits, giving 536,870,912 total addresses and 536,870,910 usable hosts.
/3 at a glance
| Property | Value |
|---|---|
| CIDR prefix | /3 |
| Subnet mask | 224.0.0.0 |
| Wildcard mask | 31.255.255.255 |
| Total addresses | 536,870,912 |
| Usable hosts | 536,870,910 |
| Host bits | 29 |
How it is calculated
A /3 sets the first 3 bits to 1 (network) and the remaining 29 bits to 0 (host). Usable hosts = 229 − 2 = 536,870,910.
The wildcard mask 31.255.255.255 is the inverse — used in Cisco ACLs and OSPF network statements.
Frequently asked questions
What is a /3 subnet mask?
A /3 equals 224.0.0.0 in dotted decimal (wildcard 31.255.255.255). It provides 536,870,912 total addresses and 536,870,910 usable hosts.
How many hosts are in a /3?
A /3 has 29 host bits, so it supports 536,870,910 usable hosts.
What is the wildcard mask for /3?
The wildcard (inverse) mask for /3 is 31.255.255.255, used in Cisco ACLs and OSPF statements.
Related
Learn networking hands-on
Master IP addressing, subnetting and Cisco configuration on real lab devices with placement support at Attila Technologies, Ahmedabad.