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CIDR Aggregator

Aggregated:

  • 192.168.1.0/24

About This Tool

The CIDR Aggregator (also known as CIDR summarization or supernetting tool) combines multiple IP address ranges into the smallest possible set of CIDR blocks. This tool is essential for optimizing routing tables, firewall rules, and network configurations by reducing the number of entries while maintaining complete coverage of all original addresses. It supports both IPv4 and IPv6 networks and automatically identifies opportunities for aggregation.

How to Use

  1. Select the IP version (IPv4 or IPv6) from the dropdown
  2. Enter your CIDR blocks in the text area, one per line (e.g., 192.168.1.0/25)
  3. The tool automatically aggregates overlapping and adjacent networks
  4. Review the optimized list of aggregated CIDR blocks in the output
  5. Copy the results for use in routing configurations, ACLs, or firewall rules

Features

  • Supports both IPv4 and IPv6 address aggregation
  • Automatically merges adjacent and overlapping CIDR blocks
  • Produces the minimal set of CIDRs covering all input ranges
  • Real-time aggregation as you type
  • Handles large lists of network ranges efficiently
  • Validates CIDR notation and ignores invalid entries
  • Produces output ready for router and firewall configurations

Common Use Cases

  • Optimizing BGP routing tables by reducing route announcements
  • Simplifying firewall rules by consolidating IP address ranges
  • Reducing ACL entries in routers and switches
  • Optimizing cloud security group rules (AWS, Azure, GCP)
  • Streamlining IP address allocation documentation
  • Minimizing routing table size for better performance
  • Consolidating IP allowlists and blocklists
  • Preparing efficient network summarization for OSPF and EIGRP

Technical Details

CIDR aggregation follows specific mathematical rules to combine networks:

Adjacent Network Aggregation: Two networks can be aggregated if they are adjacent and their combined size equals a power of 2.

  • 192.168.1.0/25 + 192.168.1.128/25 = 192.168.1.0/24
  • 10.0.0.0/24 + 10.0.1.0/24 = 10.0.0.0/23

Overlapping Network Removal: If one network is contained within another, the smaller one is redundant.

  • 192.168.0.0/16 contains 192.168.1.0/24, so only /16 is needed

Aggregation Algorithm:

  1. Sort all CIDR blocks by network address
  2. Remove duplicate and overlapping ranges
  3. Identify adjacent blocks that can be combined
  4. Recursively merge blocks until no further aggregation is possible

This tool is particularly valuable for network engineers managing large-scale networks, as reducing routing table entries improves router performance and reduces memory usage.