---
title: "pcap_dropgen"
slug: "fmadio-utils-pcap-dropgen"
updated: 2025-05-06T12:01:27Z
published: 2025-05-06T12:01:27Z
canonical: "docs.fmad.io/fmadio-utils-pcap-dropgen"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fmad.io/llms.txt
> Use this file to discover all available pages before exploring further.

# pcap_dropgen

**FW:10885+ (2025Q2 release)**

pcap_dropgen is a utility designed to drop packets or duplicate packets using standard PCAP format. This can be helpful when testing analysis software on the FMADIO system.

Usage is via PCAP Linux pipes. For example

```plaintext
cat orignial.pcap | pcap_dropgen --droprate 1e9 > drop.pcap
```

The above will drop ever 1Bn packet and write the result into drop.pcap

## Reference

Command line reference

### —duprate <n>

This creates a duplicate every nth packet. Scientific notation can be used

### —droprate <n>

Drops every nth packet from the source (stdin) input on the output.

Scientific notation can be used

### —dupdist <n>

When duplicating packets, this specifies the number of packets after the orignial packet the duplicate packet is inserted.

Example setting of 5

Packets 1, 2, 3, 4, 5, 6, 7, 2 (distance of 5 packets from the original packet), 8, 9, 10

---

## Examples

### Duplicate every 1000th packet

Example code

```plaintext
cat original.pcap | pcap_dropgen --duprate 1000 > duplicate.pcap
```

### Drop every 1000th packet:

Example code

```plaintext
cat original.pcap | pcap_dropgen --droprate 1000 > drop.pcap
```