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Add unmanaged switch to Catalyst: how to set up the port?

Flavio Boniforti

Hello everybody.

As I'm quite new to this kind of things, I'll ask here for help.

Needing to temporarily add a switch to an existing network, I have a 5-port unmanaged switch which I should connect to a Catalyst switch. My question is: how would I need to configure the Catalyst port on which I'll connect the unmanaged switch?

My thoughts have been so far:

  • as the switch is unmanaged, it is probably not supporting STP and thus not sending nor receiving BPDUs, right?
  • if the above is correct, I do not need to set the Catalyst port to be a trunk-port, right?

What would be the minimum configuration to apply to that Catalyst port?

TIA and kind regards,



Accepted Solutions

It will put it in error-disabled state only if the switchport port-security maximum is configured on the port. By default it's not so you shouldn't have a problem.

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The configuration which I wrote is for the Catalyst switch. You will connect the unmanaged switch to the port configured in this ways. You do not configure unmanaged switch.

I am suggesting "access mode" because:

- I assume that you will connect PCs to that switch and all those PCs (let's say 8) are supposed to access your production LAN - for example vlan 3. In such case the access mode is the way to go.

- Unmanged switch does not support trunking - this is what I think but I did not check it - so do not call me on that one.

The bpduguard is just in case. You do not have to put it. If you configure it and in the future someone will connect switch which will be able to generate BPDUs the port will shut itself down - and you will know about it. You do not have to configure it.

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Leo Laohoo
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1.  Disable STP Portfast on the port.

2.  Try with trunk first.  If it doesn't work then use access port.

Hello and thanks for your feedback.

Wouldn't an access port shut down, if it would "see" more than 1 MAC Address?