Editing the qos.cfg file in VX Enterprise and VX Prime+

Updated 1 month ago by Shaun Dolan


The qos.cfg file is an advanced method for modifying the following parameters:

  • IEEE 802.1p priority code point
  • IEEE 802.1Q VLAN tag
  • IP Time to Live (TTL) value
  • IP DiffServ code point (DSCP)
  • Set IP Don't Frag (DF) bit (Standard Stereo & AES67 streams only)
  • Receive buffer size in microseconds (2000-20000, AES67 streams only)

This functionality is only available in VX Enterprise and VX Prime+.


VX software version 1.1.1 or above for VX Enterprise or VX Prime+ is required to edit qos.cfg.
  1. If you do not already have it installed, download, install, and open WinSCP.
  2. Enter the correct parameters for the new session:
    File protocol: SCP
    Host name: the IP address of your VX; in the example below
    Port number: 22
    User name: root
    Password: element
  1. Click Login, and say Yes to any prompts about trusting an unknown host.
    You are now logged in to the VX filesystem (right pane). You can also see your computer's file system (left pane).
    Please do not attempt to make other changes to system files or settings other than described here. VX is designed as an appliance and a specific hardware environment is expected. Any other changes made can have unexpected results and may require factory service to resolve. Issues resulting from changes made outside of those specified here are not covered by the warranty.
  2. On the right pane, double click the "Go up" icon to navigate to the root of the file system:
  1. On the right pane, navigate to, etc > local > telos_vx by double-clicking each folder.
  2. Open the file qos.cfg, or create it if it doesn't exist.
  3. Use this document as a guide in composing the qos.cfg file per your requirements.
  4. Save this qos.cfg file and reboot the VX (via the web UI Status page).

The qos.cfg options are not yet exposed in the web UI as they are needed in less than 1% of installations.

Let us know how we can help

If you have further questions on this topic or have ideas about how we can improve this document, please contact us.

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