Spanning tree practice lab question.

[Reprovoid]

Hi.I'm doing a practice lab for spanning-tree but I'm confused about the output of the sh spanning-tree command.I've attached an Image.

  I don't understand how the cost to root Is 4 for both vlans when the route to the vlan 12 root switch crosses 2 segments with gigabit ports.

[Peter Paluch]

Hello,

Is this a simulator of some sort? The displayed screenshot does not display all necessary data. From what is visible it is clear that the root bridges for VLAN1 and VLAN12 are different, yet SW3 uses the same root port towards both of them. It is theoretically possible that the costs for VLAN12 have been manually modified (for example, set to 2 on SW3/SW1 and SW1/SW2 links, resulting in the overall cost of 4 towards the SW2 as the root bridge for VLAN12).

Best regards,

Peter

[Reprovoid]

Hi.Thanks for taking a look.It Is a simulator yes.It seems to be an error.

[johnlloyd_13]

Hi,

Could you share what sim you're using or is there any site? Thanks!

Sent from Cisco Technical Support iPhone App

[Reprovoid]

Hi.Thank you for taking a look too!

  It's the CCNA 640-802 Network Simulator , Second Edition V1.4000 PearsonITcertification.