| Exam 300-115 | Question id=1392 | Layer 2 Technologies |
Refer to the exhibit.
switch#show run
interface FastEthernet0/13
spanning-tree cost 1000
!
interface FastEthernet0/14
spanning-tree cost 1000
!
interface FastEthernet0/15
spanning-tree cost 1000
!
interface FastEthernet0/20
spanning-tree cost 2
!
interface FastEthernet0/21
spanning-tree cost 1
!
All ports are members of VLAN 10. Considering the default cost of upstream bridges to the root bridge is equal, which option will be the new root port for VLAN 10?
| A. |
interface f0/13 | |
| B. |
interface f0/14 | |
| C. |
interface f0/15 | |
| D. |
interface f0/20 | |
| E. |
interface f0/21 |
Root Port election on each bridge
Each (non-Root) bridge has exactly one Root Port, which represents the best path to the Root Bridge.
* Total Path Cost to root - lowest prevails (local Root Port cost added upon receipt of Configuration – PDUs on that port, from the direction of Root Bridge)
* Connected Bridge ID - lowest prevails
* Connected Port ID (Port Priority + Port#) - lowest prevail–
* Local Port ID - lowest prevails
In this case, fa0/21 has the lowest cost, so it will be the root port