Advanced tools and tips for the Optus Sagemcom F@st 3864 broadband router
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This repository is a collection of tools and tips for the Optus Sagemcom F@ST 3864 broadband modem.

Getting Access to Advanced Configuration Options

The advanced features of the modem are not accessible by default and require you to login as the admin user to be able to view and modify them.

There are a number of ways you can obtain the admin password, with some methods depending on the firmware version your modem is running.

Factory Default Passwords

Listed below are the factory default passwords set on Optus' devices. These get automatically changed from the defaults when you connect the device to the Internet for the first time.

Leave the modem WAN/DSL ports disconnected if you want to access the modem using these passwords.

Stick a paperclip in the RESET button for 5 seconds to reset the modem to factory default configuration.

The passwords differ between modem models and firmware verions so try each one below until it works.

user password url
admin Y3s0ptus http://admin:Y3s0ptus@
admin 0ptU%1M5 http://admin:0ptU%1M5@
admin 8PTu5W@C http://admin:8PTu5W%40C@
optus * optus http://optus:optus@

* Not an admin account

Getting the admin Password Prior to Software Version 8.353.1_F@ST5350_Optus

Getting the admin user password prior to firmware version 8.353.1_F@ST5350_Optus such as version 7.253.2_F3864V2_Optus.

Open a web browser to and navigate to Managment / Access Control and view the source of the righthand part of the page. Near the top of the page you will find a line something like this:

pwdAdmin = "XXXXXXX";

This is the admin user password.

If you now open your browser to and enter the admin user and password details found you will enable the advanced configuration menus.

Getting the admin Password All Versions

From firmware version 8.353.1_F@ST5350_Optus access to the advanced settings was disabled, as was the ability to view the admin password in the Access Control page.

However, thanks to some reverse engineering done by Matty123123 at the forums there is a way to decrypt the configuration file obtained when you download the backup settings from the router.

Open a web browser to and navigate to Managment / Configuration / Backup and download the backupsettings.conf file.

Next download a copy the the script included in this repository.

Set up Linux

Install the dependencies:

$ sudo pip install pycryptodome

Set up Windows

On Windows systems will need to download and install python 3.5. Make sure you check the box to add Python to your PATH in the installer.

Then open a DOS or PowerShell command shell and install the pycrypto module:

pip install pycryptodome


Download the script and you backupsettings.conf from your modem and put them in the same directory.

Decrypt the Settings

On Linux/Unix-like systems run:

$ python backupsettings.conf

or on Windwos:

> python.exe backupsettings.conf

This will produce a new file called backupsettings.conf.txt. Search this file for the lines:


The password is base64 encoded so to decode it copy it into the following command line:

$ echo XXXXXXXXXXXX== | base64 -d

Accessing the Advanced Settings

To access the advanced menus enter the following URL with your router's admin password into your browser:


Credit goes to Matt Goring for his original Windows configuration decryption tool on which I based my python script.

Uploading a Modified Configuration

Once you have obtained a plain text version of the configuration you can then modify it and upload it to the device.

Open a web browser to and navigate to Managment / Configuration / Update and upload your modified the backupsettings.conf.txt file.

There is no need to encrypt the file as the router will accept plain text files.

Enabling Telnet

Enabling telnet allows you to explore the device a little more and customize it further from the Linux command line.

To enable telnet you need to modify a plain text copy of the configuration to include the line:


The configuration may already contain the line above but it is set to FALSE so just change it to TRUE.

If it is missing the line then add it after the following line:


Then upload the modified configuration.

You will now be able to telnet to and login using the username admin and the password you obtained earlier. Once you are logged in you are put into a restricted shell so type sh to drop into a BusyBox Linux shell.

Putting the device into bridge mode

ADSL2 Connections

Follow the instructions in the PDF to put Optus F@st 3864 modem into bridge mode. Original credit to Ray Haverfield.


  • Use the instructions above to obtain your admin password rather than those in the PDF.

NBN FTTN/VDSL Connections

The NDN FTTN/VDSL steps are similar to ADSL:

  1. Backup your existing configuration in case you want to revert to it later.
  2. Factory reset the modem by hold a paper clip in the reset hole at the back of the modem until all the lights flash and it reboots.
  3. Use the instructions above to obtain your admin password.
  4. Open a web browser to and login as admin with the password obtained in the previous step.
  5. Navigate to Advanced Setup / WAN Service. Look for the row in the table with interface ptm0.1 and description ipoe_0_1_1.0. Select the Remove checkbox for that row only and click the Remove button. This will remove the non-bridged NBN FTTN VDSL WAN interface.
  6. Navigate to Advanced Setup / WAN Service and click the Add button. This will start a wizard-like set of forms for configuring the WAN Service Interface.
  7. On the first page select a layer 2 interface for the service. Select ptm0/(0_1_1) and click Next.
  8. On the next page select the WAN service type Bridging. Do not change any other settings. Click Next.
  9. On the next page is a summary of the settings. Click Apply/Save.
  10. Next you will need to disable DHCP on the modem so that the alternative routing device you are bridging can get a public IP via DHCP. Navigate to Advanced Setup / LAN and select Disable DHCP Server and click Apply/Save.
  11. Next you should disable wireless. Navigate to Wireless and uncheck the Enable Wireless box. Click Apply/Save.
  12. Then reboot the modem by clicking the reboot button in the status widget at the top right.

Once the modem has rebooted and the VDSL connection is established you can connect your other router's ethernet WAN interface into the Optus modem. Configure your other router to use DHCP on the WAN interface and it should get an IP address handed out to it from upstream server at Optus. If you get a 192.168.0.x IP address then you haven't disabled DHCP on the Optus F@st 3864 modem and you'll need to connect a PC to it again to do that.

Note: Once you have disabled DHCP on the F@st 3864, if you ever need to make changes to it you will need to connect a computer to it with an ethernet cable and manually configure and IP address on your computer. Use or higher. Then you will be able to browse to to make changes.

Note: You can test if bridging is working by plugging a computer using an ethernet cable and having DHCP configured. However, I strongly discourage doing this unless you know what you are doing and are sure that your computer's operating system is 100% up to date with all operating system security patches. Your computer will not have time to check for patches and update before you will be scanned and hacked within minutes. You have been warned!

Coming Soon...

  • Dumping the firmware
  • Full list of URLs
  • PSI configuration decoder