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DrayTek routers that support Quality of Service (QoS) can be configured in a variety of ways. A useful application is to configure QoS to prioritise VPN traffic so that the VPN will still have bandwidth available to it when there is heavy demand for the WAN connection.

A general guide on Quality of Service is avaiable here but the guide below provides a step by step explanation of how to configure QoS to prioritise VPN traffic for the scenario in the network topology shown below:

In this setup VPN traffic will be assigned to Class 1 and it will then be allocated a reserved bandwidth ratio of 80% so that it is able to reserve upto 80% of the bandwidth if required. Unused bandwidth allocation is released for other classes to utilise but this unused bandwith allocation is automatically redirected back Class 1 if it is needed. A QoS class is permitted to exceed its bandwith allocation (it does not act as an enforced bandwidth cap) provided the other classes do not take up their assigned bandwidth allocation. Class 1 is the highest priority QoS class and as such has first refusal on spare bandwidth that isn't being used by other classes bandwidth reservation (Class 1 > Class 2 > Class 3 > Others).

Any traffic that does not match a class rule is assigned into the 4th class, Others.

How to setup QoS for VPN


Go to Bandwidth Management >> Quality of Service. To create a new rule, choose a class and click Edit.


2.Set up Class Rule, and click OK.

a.Enter Name for the class.
b.Click Add to create a new rule.

3.Edit rule, and click OK.

a.Tick ACT.
b.To set Local Address, click Edit.


i.Choose a Address Type (Here we use Subnet Address).
ii.Enter Start IP Address and Subnet Mask.

c.To set Remote Address, click Edit.


i.Choose a Address Type (Here we use Single Address).
ii.Enter Start IP Address.

d.Choose ANY for Service Type.
NOTE: We choose ANY because the destination port is not predictable

4.Go to Bandwidth Management >> Quality of Service, and click Setup.

NOTE: After finishing the configuration, remember to click OK.

5.Set up the configuration, and click OK.

a.Check Enable the Qos Control, and choose OUT.

b.Enter a number for WAN Outbound Bandwidth based on the WAN throughput available, and select a unit.

c.Enter a number for Reserved_bandwidth Ratio.

6.To check the Online Statistics, go to Bandwidth Management >> Quality of Service, and click Status.