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THE FEUTEX TOOLKIT

NAT Source Port Capacity

Estimate public address count for same-destination connections using a specified usable port range.

Networking workspace● Runs in your browser
01 Your input
02 Your result
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FormulaUsable ports per address = Math.floor((last-first+1)*(1-reserve/100)); Required source addresses = Math.ceil(connections/Math.floor((last-first+1)*(1-reserve/100)))

Made for real tasks

  • Estimate public address count for same-destination connections using a specified usable port range.
Explore step-by-step workflows →

Worked example

Inputs

Simultaneous same-destination connections
200000 connections
First usable source port
1024 port
Last usable source port
65535 port
Port reserve
10 %

Expected results

Usable ports per address
58060 ports
Required source addresses
4 addresses

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

  1. Enter simultaneous same-destination connections, first usable source port, last usable source port, port reserve in the displayed units.
  2. Calculate the scenario, then compare it with measurements before changing a system.

Try this example

{
  "connections": 200000,
  "first": 1024,
  "last": 65535,
  "reserve": 10
}

Accuracy and scope

Same remote tuple and exclusive source ports; real NAT reuse, timeouts and platform quotas differ.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.