Online CIDR Converter - CIDR to Subnet Mask / Wildcard / IP Range
CIDR → Subnet mask / Wildcard mask / IP address range
About CIDR
CIDR (Classless Inter-Domain Routing) expresses a network as IP/prefix-length, e.g. 192.168.1.0/24 equals the mask 255.255.255.0 with wildcard mask 0.0.0.255 and usable range 192.168.1.1-192.168.1.254.
Continue With
Once you have the network range, continue with the IP Calculator to verify specific address details, test host reachability within the range with the Ping Test, or use the Subnet Calculator for more complex subnetting plans.
FAQ
What does CIDR notation mean?
CIDR (Classless Inter-Domain Routing) expresses a network as "IP address/prefix length", e.g. 192.168.1.0/24, where /24 means the first 24 bits are the network portion — equivalent to the subnet mask 255.255.255.0 — replacing the traditional class A/B/C address scheme.
What subnet mask does CIDR /24 correspond to?
/24 corresponds to the subnet mask 255.255.255.0, wildcard mask 0.0.0.255, with a usable range from x.x.x.1 to x.x.x.254 — 254 addresses. Common pairings: /16 = 255.255.0.0, /8 = 255.0.0.0, /28 = 255.255.255.240.
What is a wildcard mask used for?
Wildcard masks are mainly used in Cisco ACLs and OSPF routing configuration; a wildcard mask is the bitwise inverse of the subnet mask. For example 255.255.255.0 has a wildcard of 0.0.0.255.
How do I convert between CIDR and a subnet mask?
The CIDR prefix length is the number of leading 1s in the subnet mask. For example /26 means the first 26 bits are 1, giving 11111111.11111111.11111111.11000000 = 255.255.255.192. Enter a CIDR here and this tool derives the matching mask automatically.
How is CIDR used in firewalls and ACLs?
Firewall rules and ACLs commonly use CIDR to express IP ranges. Allowing 192.168.1.0/24 permits traffic for the whole 192.168.1.0-192.168.1.255 segment, which is more concise and efficient than listing IPs one by one.