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IP in CIDR

Check whether an IPv4 or IPv6 address belongs to a CIDR network.

What this tool does

IP in CIDR checks whether one address falls inside a network range such as 8.8.8.0/24 or 2001:db8::/32.

It is useful for firewall allowlists, routing checks, abuse triage, and validating whether an address matches a provider or customer network. The CIDR notation guide explains the slash prefix.

CIDR notation explained Learn how slash prefixes describe IP network ranges. CIDR calculator Normalize a network and inspect first, last, mask, and broadcast values. Range to CIDR Convert start and end addresses into covering CIDR blocks. Subnet splitter Split a larger network into smaller child networks.