Network tool

IP in CIDR

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

Result: outside network.

IP address: 8.8.9.1
Network: 8.8.8.0/24
Inside network: No
IP version: IPv4
Network version: IPv4
First address: 8.8.8.0
Last address: 8.8.8.255
Total addresses: 256

Reference

Output fields

Inside network: The direct yes/no result for whether the address is inside the CIDR range.
IP version: IPv4 and IPv6 addresses must be checked against a network of the same version.
First address: The lower bound of the network range used for the comparison.
Last address: The upper bound of the network range used for the comparison.

Overview

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.

Examples

Example checks

Inside network

8.8.8.8 in 8.8.8.0/24 Returns yes because 8.8.8.8 is between 8.8.8.0 and 8.8.8.255. Check inside example

Outside network

8.8.9.1 in 8.8.8.0/24 Returns no because the address is outside the calculated range. Check outside example

Results

How to read results

The inside-network value is the direct yes/no answer. The first and last address show the bounds used for the comparison, so you can verify the result against a firewall rule, vendor list, or routing note.

Boundaries

Limits

The IP address and CIDR network must use the same IP version. This tool checks mathematical range membership only; it does not verify ownership, reputation, geolocation, or whether traffic is currently routed from that network.

Next steps

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.