Root Port Question?

itisyeah

Is the root port of a switch ALWAYS the port that is directly connected to the Root Bridge?


I have read that the root port is the path with the lowest cost (bandwidth) to the root bridge, but I have also read that if the switch connects directly to the root bridge, then that directly connected port will the root port?
I have seen conflicting info on this, could someone confirm?

acidsatyr

It's not conflicting info; Every bridge (except root bridge itself) has one port which is closest to getting to the root bridge - that's the root port (closest as in - with the smallest cost compared to other ports on bridge). Weather the network segment connects that bridge with the root bridge directly or not doesn't matter.

Morty3

If a root port is the one closest to a bridge but not necessarely is directly connected, what is then a designated port?

acidsatyr

A designated port is a port with lowest cost to the root bridge on a given network segment. Each network segment has only one designated port.


{SW1}r

---

d{SW2}r

---

d{root bridge}

Picture above - 2 network segments, one between switch 1 and switch 2, and other between switch 2 and root bridge.
Notice root port (r) on both SW1 and SW2 -> those are the ports which are closest (in term of cost) to root bridge.
Now notice 2 designated ports (d), one on each network segment. They are ports on segment with lowest cost to root bridge.

In other words, think of root port as function of each switch, and designated port a function of every network segment, both with the lowest cost.