VLAN Configuration changed automatically on Cisco SG300-28 Switch

[malay]

Hello,

I am using Cisco SG300-28 Switch. Few days ago, the Network connectivity was down on one of the trunk port. I found an abnormality on that port in running configuration of the switch.

In startup configuration, the port configuration was as under.

##########################

!
interface gigabitethernet5
description CCTV_ControlRoom
switchport trunk native vlan 10

switchport trunk allowed vlan add 2-6

############################

But, in running configuration, I found that it was changed automatically as under !!!

#############################

!
interface gigabitethernet5
description CCTV_ControlRoom
spanning-tree link-type point-to-point
switchport trunk allowed vlan add 2-6,85-90
macro description switch
!next command is internal.
macro auto smartport dynamic_type switch

#############################

Since native VLAN on the port was changed from 10 to 1 (default), the network connectivity was lost.Some unnecessary VLAN were also allowed in the trunk port. After rebooting the switch, the problem was resolved.

My question is : How a Switch can modify its static VLAN configuration automatically which creates a lot of problem? How to prevent this?

I would like, if any expert throws some light on the issue & suggests me a solution.

Thanks.

[Mohsin Alam · Accepted solution]

you have the Auto Smart port feature enabled. It can be Enabled/Disabled globally.

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[malay]

Thanks for your reply with a solution.

By the way, why SmartPort feature changes our running configuration ? Is it not unsafe mechanism ? Also, who is responsible for such unwanted activity?

Please share your views.