Calculator Form
Example Data Table
The sample below shows a clean case where four aligned /48 routes collapse into one /46 summary.
| Input Route | Prefix | Coverage Start | Coverage End | Expected Exact Summary |
|---|---|---|---|---|
| 2001:db8:1200::/48 | /48 | 2001:db8:1200:: | 2001:db8:1200:ffff:ffff:ffff:ffff:ffff | 2001:db8:1200::/46 |
| 2001:db8:1201::/48 | /48 | 2001:db8:1201:: | 2001:db8:1201:ffff:ffff:ffff:ffff:ffff | |
| 2001:db8:1202::/48 | /48 | 2001:db8:1202:: | 2001:db8:1202:ffff:ffff:ffff:ffff:ffff | |
| 2001:db8:1203::/48 | /48 | 2001:db8:1203:: | 2001:db8:1203:ffff:ffff:ffff:ffff:ffff |
Formula Used
1) Network Boundary
Network bits remain unchanged. Host bits become zero. Normalized Network = Address AND Prefix Mask.
2) Common Prefix Length
CPL equals the count of identical leading bits between the lowest covered address and highest covered address.
3) Summary Block Size
For a prefix p, block size = 2128 - p addresses. Smaller prefixes represent larger summarized coverage.
Exact summarization first merges overlapping or contiguous coverage, then converts every merged range into the smallest possible set of valid CIDR blocks.
Single covering supernet uses the first common bits shared by the minimum and maximum covered addresses, then fills remaining bits with zero.
How to Use This Calculator
- Paste one IPv6 CIDR route per line, or separate them with commas.
- Choose whether duplicates should be removed and contiguous coverage merged.
- Enable normalization if you want host bits converted to valid network boundaries.
- Click Summarize Routes to generate exact summary blocks and the covering supernet.
- Review the normalization report, graph, and reduction metrics.
- Download the output as CSV or PDF for design reviews, routing change logs, or audits.
FAQs
1) What is IPv6 route summarization?
It combines contiguous IPv6 networks into fewer advertisement blocks. The goal is smaller routing tables, cleaner policies, and easier operational management.
2) Does summarization always produce one route?
No. Disjoint or misaligned coverage may require several exact summary blocks. One covering supernet can still be shown, but it may include unused addresses.
3) Why were some routes normalized?
A route such as 2001:db8::1/64 is not a clean network boundary. Normalization converts it to 2001:db8::/64 before aggregation.
4) What does common prefix length mean?
It is the number of leading bits shared by the lowest and highest covered addresses. That shared bit span determines the broadest possible supernet.
5) Why can a supernet include extra addresses?
A single supernet must follow binary alignment rules. When input coverage is uneven, the nearest valid supernet can be wider than the exact union.
6) Can I mix /48, /56, and /64 routes?
Yes. The calculator normalizes each route, merges covered ranges, and then rebuilds the smallest valid exact CIDR set from those ranges.
7) What does the Plotly graph show?
It compares prefix counts before and after summarization. That makes it easy to see whether many small routes collapsed into fewer broader blocks.
8) When should I avoid summarizing routes?
Avoid it when different routes need separate policies, failover paths, security handling, or traffic engineering. Over-broad summaries can hide important operational distinctions.