CIDR and Useable IPs - ServerMania

When an IP address range is assigned to a dedicated server, its done in CIDR format.

Using 138.128.17.168/29 as an example, below is a breakdown of the IP addresses in the CIDR format. The amount of IPs available will change based on the range size.

Example 138.128.17.168/29 CIDR

138.128.17.168 Network
138.128.17.169 Gateway
138.128.17.170 Useable
138.128.17.171 Useable
138.128.17.172 Useable
138.128.17.173 Useable
138.128.17.174 Useable
138.128.17.175 Broadcast

Cheat Sheet

Range Netmask Useable IPs

/29 255.255.255.248 , 5 usable addresses
/28 255.255.255.240 , 13 usable addresses
/27 255.255.255.224 , 29 usable addresses
/26 255.255.255.192 , 61 usable addresses
/25 255.255.255.128 , 125 usable addresses
/24 255.255.255.0 , 253 usable addresses

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