CIDR Ranges for Firewall Rules
Convert IP ranges to CIDR notation for firewall allow/deny rules and ACLs.
IPv4 subnetting reference. /31 and /32 are handled per RFC 3021 (point-to-point and single-host). All math runs locally in your browser.
Firewall tips
Firewall and security-group rules use CIDR notation. Confirm a range covers exactly the IPs you intend — no more, no less.
The wildcard mask is what Cisco ACLs use (inverse of the subnet mask) — this tool shows both.
To allow a single host, use /32. To allow a whole office subnet, match its network CIDR exactly to avoid over-permitting.
Cómo funciona
¿Por qué usar el nuestro?
Also check out…
Subnet Planning for Network Admins
Plan IP allocation, calculate usable hosts, and si
Subnetting Practice for IT Students
Check your subnetting homework and CCNA practice p
Home Lab & Self-Hosting Subnets
Plan IP ranges for your home network, VLANs, Docke
Plan Cloud VPC CIDR Blocks
Size AWS/GCP/Azure VPC and subnet CIDR ranges befo