Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

If a network has only one switch, does STP take place ? Also, if it does, do the ports of the switch become designated ?

Thank you.

share|improve this question
up vote 5 down vote accepted

Q: If a network has only one switch, does STP take place?

A: Yes. STP operations occur as they normally would, although no topology is discovered or built due to there being only a single switch. The switch will send BPDU's out any connected ports but connected devices that aren't switches will drop/ignore the BPDU's.

Q: Do the ports of the switch become designated?

A: Yes. All ports on the Root bridge that are connected to other devices, whether they be other switches or any other network device will become designated ports, since all ports on the Root bridge are designated ports.

Here's the output of the "sh spanning-tree" command from a single Cisco Catalyst 2950 switch with a single workstation connected to port Fa0/1:

enter image description here

share|improve this answer

It depends if you have configured it or not. I would enable it because you never know what the feature might bring (new switches). Also never underestimate the power of incompetence (someone taking a cable and putting both ends in the switch.).

share|improve this answer
I was talking about Cisco switches. As I know, there STP is enabled by default. So a Cisco switch would have the STP algorithm going and become de Root Bridge? Also, do the ports become designated ? I thought that only ports to other switches can become designated. – coredump Jan 20 '13 at 13:39

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.