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Supernet Aggregation Calculator

Work out supernet aggregation instantly with clear inputs, formula shown and shareable results.

About Supernet Aggregation Calculator

Aggregation replaces several consecutive prefixes with one shorter prefix. Combining 2^b equal-size networks shortens the mask by b bits, and the aggregate only advertises correctly if the first network sits on a boundary that is a multiple of the aggregate size. Any addresses inside the aggregate that you have not actually allocated are advertised anyway, which is why alignment and waste both matter.

Formula

Aggregate prefix

b = ceil(log2(member count)); aggregate prefix = member prefix - b; aggregate network = first network AND aggregate mask

Worked example

With the default values below, Supernet Aggregation Calculator returns Aggregate route of 192.168.8.0/22. Change any input above and every figure here is recalculated in your browser.

Inputs used

First member network
192.168.8.0
Member prefix (/n)accepts 1–32 bits
24 bits
Number of consecutive networksminimum 1
4

Results

Aggregate route
192.168.8.0/22
Aggregate prefix
22 /n
Addresses covered by the aggregate
1,024
Addresses covered but not allocated
0

Step by step

  1. 1Values used
  2. 2Aggregate prefix
  3. 3Aggregate route= 192.168.8.0/22
  4. 4Aggregate prefix= 22 /n
  5. 5Addresses covered by the aggregate= 1,024
  6. 6Addresses covered but not allocated= 0

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What happens if the block is not aligned?

The aggregate silently covers addresses that belong to someone else, which can black-hole traffic. Always verify that the first network equals the aggregate network address.

Is aggregating a non-power-of-two count possible?

Not with a single prefix. Round up to the next power of two and accept the extra coverage, or advertise two or more aggregates of different lengths.

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