CIDR and Useable IPs

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