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Engineering tools / IPv4 planning

Split and summarize CIDR blocks

Combine adjacent or overlapping IPv4 ranges into the smallest exact set of routes, or split one block into two equal children. All calculations stay in this browser.

Exact route summarization
Paste comma-, semicolon- or newline-separated IPv4/CIDR blocks (up to 256). Example data only; no routes are applied.

Use network addresses or host/prefix notation; host bits are normalized. Gaps are never filled.

Exact address coverage

2 inputs → 1 CIDR block, covering 512 unique addresses.

  • 192.168.10.0/23
Binary subnet split
Split one IPv4 block into two equal adjacent child blocks. A /32 cannot be split.

Example: a /24 becomes two /25 networks. This is address math, not a DHCP or router change.

192.168.10.0/25

192.168.10.128/25

How this works

Inputs are normalized, overlapping and adjacent address ranges are united, and the result is covered with the largest aligned CIDR blocks that add no addresses. This is exact range math, not a recommendation to advertise a route, and it does not check your live topology, security policy, NAT or provider restrictions.

Source: RFC 4632 — Classless Inter-domain Routing. Generated JSON contains only the CIDRs you entered and calculation metadata. Avoid sharing internal plans without authorization. PDF export is not offered until official pdfcn rendering is validated.