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CIDR

CIDR Merger

Normalize and merge IPv4 CIDR lists into a minimal set.

Input
Provide a multiline list of IPv4 CIDRs.

Processes up to 5000 lines.

All calculations run locally in your browser.

Output
Minimal merged CIDR set

Valid input

0

Output

0

Reduction

0.0%

What

CIDR Merger definition

CIDR merging removes duplicate/contained ranges and combines adjacent blocks when possible.

Cases

Use Cases

1

Simplify firewall ACL rules

2

Remove duplicate network ranges

3

Clean large CIDR inventories

How To

How to merge CIDR lists

Paste CIDRs and reduce them to the minimal representation.

1

Paste CIDRs

Enter one IPv4 CIDR per line.

2

Run merge

Start merging to normalize, deduplicate, and combine ranges.

3

Review output

Check reduced output count and copy merged CIDRs.

Knowledge

Understanding CIDR merging

Why merge CIDRs
Reducing rule count makes ACLs easier to review and maintain.
Normalization
Normalizing to network address form enables reliable comparisons.
Containment reduction
Subnets fully covered by broader ranges can be eliminated safely.
Adjacent supernet merge
Two sibling networks can merge only if they are contiguous and aligned.
Policy caution
Always verify merged output still matches your intended access policy.

FAQ

CIDR Merger FAQ

What input format is supported?
Only IPv4 CIDR notation (for example, 10.0.0.0/24).
How are duplicates handled?
Duplicate normalized CIDRs are removed automatically.
How are contained ranges handled?
If a larger block fully contains a smaller one, the smaller one is dropped.
When can adjacent ranges merge?
Adjacent blocks with the same prefix merge only when supernet boundaries align.
How are bad lines reported?
Each invalid line is reported with line number and content.
Is there an input cap?
Yes. A line limit protects browser resources.
Does it support IPv6?
Not in this version. IPv4 only.
Is data uploaded anywhere?
No. Merging runs entirely in-browser.

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CIDR Merger