Installation Guide

It is a good idea to print out these instructions before proceeding, especially if you’re flashing the firmware in your sole router. If your router has already been flashed with CeroWrt firmware, so you can proceed to Step 1 (“Configuring and Installing the Router”) below.

Step 0. Flashing the router

Please see the CeroWrt flashing instructions for how to install the current CeroWrt build on your bismark:WNDR3700v2 or WNDR3800 Router from your platform of choice (Windows, OS X, Linux).

Step 1. Configuring and Installing the Router

  1. Power on your router. The router should boot in under two minutes. It takes a lot longer the first time after flashing (sometimes six or seven minutes) as it has to fully check flash for errors. The router itself comes up on The router serves IP addresses on networks by default. (see why .42?)
  2. Connect to your router. Plug in a laptop or computer to one of the 4 LAN ports on the router, and refresh your laptop/computer’s DHCP IP address. Alternatively, connect via wireless by setting your SSID to “CEROwrt” (no SSID password) or “CEROwrt5”. Your machine should get an IP address from the subnet in the first case, other networks in the second and third.
  3. Configure your router’s default password. In your web browser, go to the router configuration screen at (see also why 81?). (You can ignore the warning generated by the self-signed certificate.) The default username is ‘root’, the password is ‘Beatthebloat’. Go to the System/Administration screen and enter in a new password for the router. Write this password down somewhere. The login will be “root”, and the password that you set should be something difficult. Note you can also just go to gw.home.lan for most things, once DNS is up.
  4. Secure your wireless interfaces Go to the Network->Wireless configuration page, and change the SSIDs of the various interfaces to suit your liking. (See also FAQ) Enable WPA2 encryption on the LAN interfaces, and if you wish your guest interfaces to be secured, do the same there, too. Choose unique passwords for the LAN and guest interfaces.
  5. Set your country. If you are not in the US, please set your country for both radios to the correct country in order to ensure regulatory compliance.
  6. SAVE and APPLY. At the bottom part of the Web interface, save and apply the changes (these are two distinct steps).
  7. Reboot the router. You will need to reboot the router for SSH and the Internet to come up. Reboot and connect the WAN interface to the Internet (i.e., to your DSL or Cable modem). Wait a few minutes, and refresh your laptop/computer’s DHCP address.

Important Configuration Notes:

  • The wireless interfaces default to the United States regulatory wireless spectrum by default. If you’re outside the US, you should set your country immediately to stay within your local regulations.
  • The wireless interfaces are also configured as open (no password) by default. Change the SSID and/or passwords from the web GUI, or see the Automated Configuration of CeroWrt page.
  • If you are configuring an interior router rather than your primary router, the directions Setting up an interior gateway router will be helpful. CeroWrt comes with mesh networking capability using the Babel protocol.

Step 2. Fine-tuning your SQM Settings

By default, the CeroWrt Router is configured to work pretty well at virtually all WAN link speeds. You can do even better by Setting up SQM in the router.

Step 3. That’s It!

You should now be on the Internet using the latest and greatest code from the CeroWrt Project, the Bufferbloat project, and OpenWrt .

We hope that your experience will be exceptional. Please send us your feedback and comments by registering on the wiki and posting to the bloat-devel mailing list. You can also file bugs and feature requests in our Bug Tracker

Additional steps for configuring your CeroWrt router

If this is going to be a one-time installation of CeroWrt, using the Web GUI is not very difficult. However, if you’re tracking the recent builds closely, you may have a list of settings that you wish to modify after updating the firmware. The Automated Configuration of CeroWrt page allows you to put your parameters into a file and perform them repeatably and all at once. The script lets you:

  • Update the root password
  • Set the time zone
  • Enable SNMP for traffic monitoring and measurements
  • Enable NetFlow export for traffic analysis
  • Enable mDNS/ZeroConf on the ge00 (WAN) interface
  • Change default IP addresses and subnets for interfaces
  • Change default DNS names
  • Change default wireless SSID names
  • Change the wireless security credentials

Find the script on the Automated Configuration of CeroWrt page.

A Note About Changing your Default IP Addresses

We really don’t recommend you change the default network numbering unless you know what you are doing. Seriously. Don’t mess with it.

But: If you wish to use other default IP address ranges… we recommend against using and for historical reasons. (They’re used by so many other vendors that you’re likely to run into address conflicts.)

Go to the Network screen on the router and change to suit. By default, the secured interfaces come up on the,, addresses, and the guest networks come up on and - the mesh network is disabled by default. You will also need to change the firewall rules, the /etc/xinetd.conf file and many files below /etc/chroot/named/etc/bind/

Instead of using the web GUI, it is FAR easier to change these by editing the relevant files directly on the router. As an alternative, since we have DNS, just use gw.home.lan and don’t worry about the IP addresses…. (have we scared you enough yet?) If you must change the addresses or DNS, the Automated Configuration of CeroWrt script simplifies the process.

Important: If you change the default IP address, your router’s web interface will change at this point to be whatever-you-chose:81 after doing a save and apply. You should probably reboot the router; you will also need to change the address in the url in your browser accordingly.

CeroWrt Configuration Script

This is a script that lets you reconfigure your router in a repeatable manner. It has been moved to the Automated Configuration of CeroWrt page.


To edit this page, submit a pull request to the Github repository.
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