Techkarma NetEm is a modern, browser‑based WAN emulator built on top of Linux tc/netem.
It lets you shape latency, jitter, packet loss, and bandwidth across transparent L2 bridges — perfect for testing firewalls, SD‑WAN units, routers, Starlink behaviour, 4G/5G, IPS systems, failover logic, and more.

This project is open‑core:

• Free open-source edition (this repository)
• Paid OVA appliance --- prebuilt Debian VM (ready-to-run)

➡ Official site: https://techkarma.no/ ➡ Quickstart Guide: GUIDE.md
➡ OVA Appliance: https://buymeacoffee.com/techkarma/extras

Each WAN link uses:

• Inner interface → toward your test device (FW/SD‑WAN/router)
• Outer interface → toward upstream/ISP side
  Bridges (br-wan1, br-wan2) are created automatically.

Clean UI with sliders for:

• Delay (ms)
• Jitter (ms)
• Packet loss (%)
• Bandwidth limit (Mbit/s)

Give each WAN link a friendly name:
Fiber primary, Starlink, 5G backup, etc.

Under the hood:

• tc qdisc netem for latency/jitter/loss
• tbf (token bucket filter) for bandwidth
• Linux bridges for transparent forwarding

Optimized for:

• Fortinet
• Cisco
• Juniper
• Palo Alto
• SD‑WAN platforms
• Starlink testing
• Failover tuning
• IPS/IDS behaviour analysis

        +----------------------+
        |  Test Device (FW)    |
        +----------+-----------+
                   |
               (inner NIC)
                   |
         +---------+----------+
         |   Techkarma NetEm  |
         |     br-wan1        |
         |   tc/netem+tbf     |
         +---------+----------+
                   |
               (outer NIC)
                   |
        +----------+-----------+
        |   Upstream Router    |
        +----------------------+

2 bridges = 2 independent WAN paths.

sudo apt update
sudo apt install -y python3 python3-venv python3-pip iproute2 bridge-utils git

cd /opt
sudo git clone https://github.com/techkarma-no/techkarma-netem.git
sudo chown -R $USER:$USER techkarma-netem
cd techkarma-netem

python3 -m venv .venv
source .venv/bin/activate
pip install flask

FLASK_APP=app.py python app.py

Then open:

http://<vm-ip>:8081/

You will see the Setup screen on first launch.

cd /opt/techkarma-netem
python3 -m venv .venv
source .venv/bin/activate
pip install flask
deactivate

File: /etc/systemd/system/techkarma-netem.service

[Unit]
Description=Techkarma NetEm - WAN Emulator UI
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
WorkingDirectory=/opt/techkarma-netem
ExecStart=/opt/techkarma-netem/.venv/bin/python app.py
User=techkarma
Group=techkarma
Restart=on-failure
RestartSec=3

[Install]
WantedBy=multi-user.target

sudo systemctl daemon-reload
sudo systemctl enable techkarma-netem
sudo systemctl start techkarma-netem
sudo systemctl status techkarma-netem

1. Go to http://<vm-ip>:8081/setup
2. Assign:
   • WAN1 alias
   • WAN1 inner
   • WAN1 outer
3. Optionally repeat for WAN2
4. Save – bridges are created automatically
5. Open Dashboard

Your links are now live.

Each WAN link is implemented as:

br-wanX
   |-- inner NIC (towards firewall/test device)
   |-- outer NIC (towards WAN/upstream)

Traffic is shaped on the inner NIC via:

• tc qdisc add dev <nic> root netem delay ... jitter ... loss ...
• tc qdisc add dev <nic> parent 1:1 tbf rate ...

Clearing shaping:

tc qdisc del dev <nic> root

Emulate:

• Bad LTE
• Moderate Starlink
• Weak backup radio
  Trigger realistic failover behavior.

Reproduce:

• Latency spikes
• Temporary packet loss
• Saturation under load

Test how your NGFW behaves under real-world poor WAN conditions.

Run:

which tc
tc qdisc show dev <nic>

Make sure no conflicting names exist:

brctl show
ip link show

Check:

sudo systemctl status techkarma-netem
sudo ss -ltnp | grep 8081

• Multiple WAN links (more than 2)
• Profile presets
• API for automation
• Automatic Starlink-behavior presets
• Import/export config
• Authentication for GUI
• Built‑in package installer

A ready-to-use VM image for: - Proxmox\

• VMware ESXi\
• VMware Workstation\
• VirtualBox\
• XCP-NG

Includes: - Debian preconfigured\

• Techkarma NetEm preinstalled\
• Web UI running automatically\
• Forced password change on first boot

Buy & auto-download:
https://buymeacoffee.com/techkarma/extras

PRs, issues and feature requests welcome.
Please open GitHub issues before large contributions.

MIT License – see LICENSE.

Made by techkarma
for people who need real WAN behavior in their labs.