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Multicast Address Range Calculator

Work out multicast address range instantly with clear inputs, formula shown and shareable results.

About Multicast Address Range Calculator

IPv4 multicast lives in 224.0.0.0/4. Inside it, 224.0.0.0/24 is link-local control traffic that routers never forward, 232.0.0.0/8 is source-specific multicast, 233.0.0.0/8 is GLOP, and 239.0.0.0/8 is administratively scoped space for private use — the multicast equivalent of RFC 1918. Carving a block gives you 2^(32-prefix) group addresses to allocate to applications.

Formula

Multicast block

groups = 2^(32 - prefix); first = base AND mask; last = first + groups - 1

Worked example

With the default values below, Multicast Address Range Calculator returns Group addresses in the block of 262,144. Change any input above and every figure here is recalculated in your browser.

Inputs used

Base group address
239.192.0.0
Group block prefix (/n)accepts 4–32 bits
14 bits

Results

Group addresses in the block
262,144
First group address
239.192.0.0
Last group address
239.195.255.255
Multicast scope
administratively scoped (239.0.0.0/8)

Step by step

  1. 1Values used
  2. 2Multicast block
  3. 3Group addresses in the block= 262,144
  4. 4First group address= 239.192.0.0
  5. 5Last group address= 239.195.255.255
  6. 6Multicast scope= administratively scoped (239.0.0.0/8)

Assumptions and limits

  • The result is derived only from the 2 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

Which range should internal applications use?

239.0.0.0/8. It is administratively scoped, so it will not clash with global assignments and can be filtered cleanly at organisation boundaries.

Why is 224.0.0.0/24 special?

Those groups are for control protocols such as OSPF and PIM. They are sent with TTL 1 and must never be forwarded off the local link.

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