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SG200-50P 50-Port Gigabit PoE Smart Switch randomly changing the configuration of VLANS on a particular port

A SG200-50P 50-Port Gigabit PoE Smart Switch is randomly changing the configuration of VLANS on a port.  

The switch has VLAN 1 as default and these additional vlans configured: 11, 100, 171, 199 and 205.  VLAN 199 is set to the voice VLAN.

One port (48) is configured as 1UP, 205T.  However the settings keep changing to 1UP, 11T, 100T, 171T, 199T, 205T. When this happens the switch prompts for the configuration to be saved.

The port is connected to a Draytek 3900 router.

What could trigger this change?

Many thanks,





3 Replies 3


Hello robert.shackleton1,

I am sorry you are experiencing this issue.  This issue probably stems from the Smartport roles.  The interface is probably negotiating as a switch/router and it allowing all the VLANs to go across the trunk link to the 3900 Router and if the switch also supports all those VLANs it will populate the trunk accordingly.

To stop this you can turn off auto smart port on the interface and manually set the interface.

Hope this helps,


Michael D.

If this post is helpful please rate or mark as correct.

Hello Michael, many thanks for your helpful and timely response.  I've done as you suggested and so far so good, however I'll keep monitoring the situation for the next week and report back. Previously the settings could stay constant for a few days and then change.

After excluding an interface from smartport, I noticed that the first time I rebooted the switch the VLAN configuration could change, but I suspect this is where it had been set by the smartport role. If I reconfigured VLANS while smartport was off on the interface, on subsequent reboots it holds fast.

Thanks again!


In case anyone has any trouble or questions on how to configure Smartports, I've found the following articles in our Knowledge Base providing some additional information and configuration support:


Smartport Properties Configuration on the 200/300 Series Managed Switches

Smartport Interface Configuration on the 200/300 Series Managed Switches


Hope this helps!


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