Cheddar Network Simulator: Installation, Licenses and Troubleshooting

This guide covers installing Cheddar Network Simulator (CNS), entering and renewing a license, and fixing the most common problems. For a full description of the program's features, see the product overview.

Installation

What you need

Windows 10 or 11 (64-bit), or Linux on x86-64 or ARM64 (for example, a Raspberry Pi 5)
A current web browser: Edge, Chrome or Firefox
About 10 MB of disk space for the program, plus room for your projects
No installer and no administrator rights

Cheddar runs on your own computer and shows its screens in your browser. Nothing is sent over the internet.

What's in the download

File	What it is
`cns.exe`	The program for Windows
`cns`	The program for Linux (x86-64)
`cns-linux-arm64`	The program for Linux on ARM64
`README.md`	The full user guide
`THIRD_PARTY_NOTICES`

Open-source components and their licenses

Windows

Unblock the zip (recommended). Before unzipping, right-click the downloaded zip file, choose Properties, tick Unblock and choose OK. Windows then won't warn about the program inside.
Unzip it into a folder of your choice, for example Documents\Cheddar Network Simulator.
Double-click cns.exe. Your browser opens Cheddar at http://127.0.0.1:8642.

If Windows shows "Windows protected your PC", choose More info, then Run anyway. This SmartScreen notice appears for programs Windows hasn't seen often; it isn't a sign of a problem. If your organization blocks the program, ask your IT department to allow cns.exe.

The tray icon. On Windows, Cheddar has no window of its own. It puts an icon in the notification area next to the clock; it may be hidden under the ^ arrow. Click it for:

Menu item	What it does
Open Cheddar Network Simulator	Opens Cheddar in your browser, for example after you close the tab
Running at …	Shows the address Cheddar is using
Open projects folder	Opens the folder where your projects and license are kept
Open log file	Opens Cheddar's log, useful when you contact support
Quit Cheddar Network Simulator	Stops Cheddar. Your work is already saved

Starting cns.exe again while Cheddar is running opens the running session instead of a second copy.

Linux

Unzip the download.
In a terminal, make the program executable once, then start it:
```
chmod +x cns
./cns
```
On ARM64, use cns-linux-arm64 instead.
Your browser opens Cheddar at http://127.0.0.1:8642.

On Linux, Cheddar runs in the terminal window. Press Ctrl+C there to stop it.

Where your files are kept

System	Projects folder
Windows	`%AppData%\CheddarNetworkSimulator` (paste this into File Explorer's address bar)
Linux	`~/.config/CheddarNetworkSimulator`

The folder holds your projects and their revisions, saved runs, your device library, your license key (license.key) and, on Windows, the log file cns.log.

Back up this folder to back up all of your work and your license.

Updating

Quit Cheddar (tray icon › Quit Cheddar Network Simulator on Windows, or Ctrl+C on Linux).
Replace the program file with the new one.
Start it again.

Your projects, revisions, runs and license carry over.

Coming from Cheddar Network Tool? Cheddar Network Simulator is its new name. The first time cns.exe starts, it stops an older copy that's still running and moves your projects folder from CheddarNetworkTool to CheddarNetworkSimulator, so everything carries over. License keys starting CNT1- keep working, and .cnt.json project files still open. Delete the old CNT.exe once Cheddar is running.

Moving to a new computer

On the old computer, quit Cheddar and copy the projects folder.
On the new computer, install Cheddar, start it once and quit it.
Replace the new computer's projects folder with the copy.

Your projects, history and license come across together. You can also export single projects with Actions › Export › Project file and import them on the other computer (Projects › Import, Tier 2 and up).

Uninstalling

Quit Cheddar and delete the program folder. To remove your projects and license as well, delete the projects folder listed above.

Licenses

Tiers

Cheddar runs as Tier 1, the free base level, until you enter a license key. A key unlocks Tier 2 or Tier 3.

	Tier 1	Tier 2	Tier 3
Devices	5	10	Up to 250
Routers / access points / switches	1 / 2 / 1	1 / 4 / 2	No limit
WAN services	Cable	Cable and fiber	All, including LEO and GEO satellite
VLANs	Untagged only	Up to 4	No limit
Longest simulation	30 s	120 s	600 s
Projects	1	5	No limit
Reports and diagram export	Watermarked	Clean	Clean
Comparing runs	No	Yes	Yes
Revision history	Last 10	Full	Full
Packet capture (Wireshark)	No	Up to 10,000 packets	Yes
Capture import and device library	No	Yes	Yes
Cable faults, WAN outages, router failures	No	Yes	Yes
WLED lighting, local servers, speed tiers	No	Yes	Yes
Router configuration and project import	No	Yes	Yes
AES67 and Dante audio, streaming players	No	No	Yes
Multi-WAN and VRRP router pairs	No	No	Yes
Aircraft hardware (Miltope nMAP2, AVDS Node)	No	No	Yes

Validate, Trace path and SQM are included in every tier.

Entering your key

Select the Tier button in the top bar.
Paste your whole key. It starts with CNS1- and is one long line of letters, numbers, dots and dashes.
Choose Activate.

The License panel then shows your tier, who the license belongs to, its key serial, its expiry date, and what each tier includes. The key is saved in your projects folder, so you enter it only once, and it carries over when you update Cheddar.

Tip: copy the key from the email or file it came in, rather than retyping it. Spaces and line breaks picked up while copying are ignored.

How long a license lasts

A license key works for one year (370 days) from the day it's issued. The License panel shows the last day.
From 30 days before it expires, a yellow banner under the top bar shows how many days are left, with an Enter renewal key button. Select × to hide the banner until the next day.
When the key expires, the banner turns red and Cheddar runs as Tier 1 until you enter a renewal key. Your projects stay saved, but projects larger than Tier 1 allows won't open or simulate until a renewal key is entered.
An expired key can't be entered again, and setting the computer's clock back doesn't extend it.
Cheddar re-checks the license once a day, so a session left open overnight notices the change.

Renewing

Enter the renewal key the same way: the Tier button, or Enter renewal key on the banner. A renewal key issued before your current one ends starts the day after it, so you don't lose days by renewing early.

To renew, contact [support email] with your key serial, shown in the License panel.

Your name on printouts

Printed reports, run comparisons and exported diagrams (PDF, SVG and PNG) carry a line such as "Licensed to Acme Aviation (key 3F9A2C)", and PDFs list the licensee as the author.

Removing a key

In the License panel, choose Remove key. Cheddar returns to Tier 1, and projects larger than Tier 1 allows won't open until a key is entered again.

Using your license on more than one computer

[Your license terms: how many computers or users one key covers.] To use Cheddar on another computer, enter the same key there, or copy the projects folder as described under Moving to a new computer.

Troubleshooting

Starting Cheddar

Problem	What to do
The browser didn't open	Click the tray icon and choose Open Cheddar Network Simulator, or browse to the address shown under Running at … (usually `http://127.0.0.1:8642`).
I can't find the tray icon	Click the ^ arrow next to the clock. Drag the icon onto the taskbar to keep it visible.
"Windows protected your PC"	Choose More info, then Run anyway. Unblocking the zip before unzipping prevents this.
My organization blocks `cns.exe`	Ask your IT department to allow it. It needs no administrator rights and makes no internet connections.
A message says Cheddar can't listen on its address	Another program is using the port. Cheddar tries ports 8643 to 8659 automatically; if all are busy, close other copies or programs and try again, or start it with a different port (see Advanced options).
"An older copy is still running"	Quit the old one from its tray icon. If there's no icon, end `cns.exe` (or `CNT.exe` for older versions) in Task Manager, then start Cheddar again.
Linux: "Permission denied"	Run `chmod +x cns` (or `chmod +x cns-linux-arm64`) once.
The page stopped responding	Cheddar may have been quit. Start it again, then reload the page.

Licenses

Problem	What to do
"This license key isn't valid"	The key was probably cut off while copying. Copy the whole key again, from `CNS1-` to the last character.
"This key expired on …"	The key is past its last day. Ask for a renewal key.
"Can't open this project"	The project needs a higher tier than the current license, or the license has expired. The message lists what's over the limit. Enter a key, or open another project.
A change is undone with a message	The change would go past your tier, for example a sixth device on Tier 1. The message says what's allowed.
Reports or diagrams are watermarked	That's Tier 1. Enter a Tier 2 or Tier 3 key.
The banner says my license is expiring	Enter your renewal key with Enter renewal key, or select × to hide the banner until tomorrow.

Projects and results

Problem	What to do
A project from a colleague won't open	It may have been made with a newer version. Update Cheddar. Importing project files needs Tier 2 or higher.
Results differ between runs	That's expected for short runs, which record only a few events. Run 120 seconds or more and try a second random seed; a real effect shows up both times.
Validate reports errors I don't understand	Select the finding: Cheddar selects the item it refers to. Trace path shows the route between two points step by step.
I deleted something by mistake	Use Actions › Undo (Ctrl+Z), or restore an earlier revision from Actions › History.

Advanced options

Run from a command prompt or terminal:

cns -addr 127.0.0.1:8642    address and port to use (default)
cns -addr 0.0.0.0:8642      let other computers on your network open it
cns -data D:\Cheddar         keep projects in another folder
cns -no-browser             don't open the browser at start
cns -version                show the version

Use -addr 0.0.0.0 with care: there's no login, so anyone on your network can open Cheddar. Windows will also ask whether to allow it through the firewall.

Getting support

your Cheddar version (shown under About)
your license serial (shown in the License panel)
the log file, if relevant (tray icon › Open log file, on Windows)
the project file, if the problem is with a design (Actions › Export › Project file)