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Description:

In certain scenarios (e.g. VoIP) it is advisable to tag the network communication with the EF flag (Expedited Forwarding), in order for this network traffic to be forwarded preferentially. If network participants cannot set the EF flag themselbes, it has to be set by a switch.  

This article describes how communication in a certain VLAN can be tagged with the EF flag on a GS-3xxx series switch.


Requirements:


Procedure:

1) Connect to the device via the webinterface, go to the menu QoS → QoS Control List → Configuration and click the "Plus" icon on the right side to open a new instance of QoS settings.

2) Adjust the conditions under which the packets are to be prioritized:

  • Port Members: Select the ports whose traffic is to be prioritized (in this example the ports 5 - 16).
  • VID: In the dropdown menu select the option Specific and in the field Value enter the VLAN whose packets are to be prioritized (in this example the VLAN 10).
  • Frame Type: In the dropdown menu select the option IPv4.

If necessary you can specify the conditions more precisely, e.g. by setting a certain source MAC address (SMAC) or a certain source address range (SIP). 

If traffic from network participants connected to another switch is to be prioritized, the uplink port to this switch has to be set as Port Member

3) In the dropdown menu for DSCP select the option 46 (EF). Thereby the specified packets from step 2) are tagged with the EF flag and forwarded preferentially.

Click Apply afterwards.

4) Go to the menu QoS → DSCP → Port DSCP.

5) Select the option Enable for Egress Rewrite for all ports a network participant is connected to, that is to receive the prioritized packets (in this example the ports 1, 27 and 28).  

Click Apply afterwards.

6) When you are finished, click the disk icon in the top right corner to save the configuration as the start configuration.

The start configuration is retained even if the device is restarted or there is a power failure.

7) Repeat these steps for further switches in the scenario, if applicable.