CIDR Merge / Supernet

Condense address blocks into optimized supernets.

Aggregation Clean list Subnet planning

Optimization

Reduce ACL size by merging contiguous blocks.

IPv4 IPv6 Supernet

What This Tool Does

This page merges compatible CIDR blocks into a shorter supernet list without changing the existing form or result grid. It is useful when you want cleaner routing or security objects while preserving valid prefix boundaries.

Inputs explained

Paste one prefix per line, choose the merge strategy, and review the resulting reduction. Strict modes avoid unnecessary expansion, while broader modes can favor smaller output lists.

How it works

The tool checks which prefixes are contiguous and align to a valid shorter prefix, then replaces them with the smallest valid merged representation.

Step-by-Step Example

If you enter 10.0.0.0/24 and 10.0.1.0/24, the tool can merge them into 10.0.0.0/23 because the boundaries align cleanly for supernetting.

Use Cases

Use CIDR merge for route summarization, ACL cleanup, and reducing the size of prefix lists before deployment.

Assumptions and limitations

The output is prefix math only. A technically valid merge may still be too broad for your routing or security policy.

Frequently Asked Questions

What does CIDR merge do?

It combines adjacent or mergeable prefixes into a smaller set of valid supernets when the boundaries allow it.

When is this useful?

It is useful for route summarization, ACL cleanup, object group reduction, and easier documentation.

What limitations apply to the output?

The output follows prefix math. It does not decide whether a broader merged block is acceptable for your routing or security policy.

Related Tools

CIDR Overlap Checker

Validate merged prefixes against existing allocations.

IPv4 Range to CIDR

Convert raw ranges before attempting merge or summarization.