How to Blackhole Traffic Using fault

This guide will walk you through emulating network severe degradation into your application using fault proxy capabilities.

Prerequisites

• Install fault

  If you haven’t installed fault yet, follow the installation instructions.

• Basic Proxy Setup Be familiar with running fault run --with-[fault] commands from your terminal.

Completely Blackhole All Traffic

In this scenario traffic is blackholed indefinitely and no packets will get through to its destination.

The client or application will attempt to connect or send data but never receive a response, eventually timing out.

• Start the proxy with blackhole fault

  fault run --with-blackhole
  

Blackhole Traffic for Specific Time Windows

Often, you want to simulate a partial outage—periods of normal traffic followed by complete blackhole intervals.

• Start the proxy with blackhole fault and a schedule

  fault run \
      --duration 10m \  # (1)!
      --with-blackhole \
      --blackhole-sched "start:10%,duration:50%;start:75%,duration:20%"  # (2)!
  

  1. Run the proxy process for 10 minutes
  2. At 10% of 10 minutes (the 1‐minute mark), start blackholing for 50% of total time (i.e., 5 minutes). Then, at 75% of 10 minutes (the 7.5‐minute mark), blackhole again for 20% of total time (2 minutes). Effect:
     • For the first minute, traffic flows normally.
     • Minutes 1–6: All traffic is blackholed (clients see no reply).
     • Minutes 6–7.5: Returns to normal.
     • Minutes 7.5–9.5: Blackhole again, finishing just before the proxy ends at 10 minutes.