From the algorithm described in P&D textbook it looks to be minimum (if all edge weights are 1). Can't find mentions on Wikipedia or a quick google search.

  • If all edge weights are 1 then every spanning tree is a minimum spanning tree. The concept of minimum spanning tree only becomes meaningful when you have varying edge weights. Oct 8, 2018 at 17:20

1 Answer 1


RSTP uses the link speed or path cost to weigh the edges (generally, 10 Tbit/s divided by the link speed). However, it does not automatically place the root bridge - that is up the configuration by the network designer.

So, no - the spanning tree is not necessarily minimum (having the least possible weight sum) although the algorithm leans that way.

A minimum tree may not even be desirable in all scenarios, depending on your traffic flows. You select your root bridge accordingly and can even change each port's priority to force the tree to become less minimal.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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