I have a questions regarding STP and i would like to know if STP is only a feature of layer 2 switches? i am on GNS3 and i am trying to enable STP but it tells me that there is no spanning tree protocol enable, i am using a switch layer 3, and i am wondering, if i have to creat a vlan, and assigne STP on interface level ?

sorry for the basic question.

i am new to networking.

  • You would need to disable it on a VLAN before you could enable it on the VLAN.
    – Ron Maupin
    Mar 19, 2019 at 15:17

2 Answers 2


A layer-3 switch is a layer-2 switch with added routing functionality - for L2, both behave exactly alike. However, when you create a routed or L3 port that port cannot participate in STP.

STP is required when a layer-2 network has redundant links (otherwise a bridge loop is created, causing a broadcast storm).


Spanning tree is a layer 2 protocol. A Cisco switch will enable it on a VLAN by default.

  • thank you and sorry for my ignorance, but and what about a cisco layer 3 switch?
    – sgt
    Mar 19, 2019 at 15:30
  • If your ports are layer 3, there is no spanning tree. If you create a VLAN and assign ports to it, then you will use spanning tree.
    – Ron Trunk
    Mar 19, 2019 at 15:35

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