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.
사용 방법
왜 저희 도구인가요?
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