STP for Dummies

Unanswered Question
Apr 29th, 2007

Anyone got any links which provide some decent understanding of STP. It is something I've never had to work with but is constantly bugging me.


I have this problem too.
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mirzaakberali Mon, 04/30/2007 - 00:45

Hi Ankur,

Can you tell me whther we can make Access Switches as Root in STP.



ankbhasi Mon, 04/30/2007 - 00:49

Hi Akber,

You can configure access switch as root switch but that is not a recommended configuration and design.

Not necessary that your access switch will have optimum path to all other switches in network , also access switches does not have much redundancy that you will plan for your core and distribution switch and there are lot more reasons it is not recommended to have access switch as root switch.

DO you have any special requirement?



*Pls rate all helpfull post

mirzaakberali Mon, 04/30/2007 - 01:01

Thanks for the information.

Please read the following info.

cs101 with vlan 483 (Access Switch )

cs102 with vlan 484/784(Server Access Switch)

cs103 with vlan 485 (Access Switch )

Cr3-hy2/cr4-hy2 is configured L3 vlans 484/784. with Routed interfaces and has ospf routing congigured .both are distribution switches.

In our network they have used one valn per switch and same switch has been pormoted as root.

No Distribution switches have been made as Root.

Please need help on this why they have done so.

Jon Marshall Mon, 04/30/2007 - 01:11

Hi Akber

Apologies for not responding to your other question, been a but busy.

The reason the distribution switches are not STP root for your vlans is that the vlans are self-contained on each access-layer switch. If you were spanning vlans across multiple switches it wouldl make sense to have your STP root as the distribution switches.

But because the vlans are self-contained all layer 2 traffic between any servers etc. will remain on the same switch. Any traffic destined for another subnet will go to the distribution switch and be routed onto the other switch.

Key thing to rememeber is that your access-layer uplinks are not trunks at all but access-ports placed into the relevant vlan.



mahmoodmkl Mon, 04/30/2007 - 03:23


In u r case i think u r running layer network,this is good design as u dnot have to think about STP issues.I think u have layer 3 links between u r access and dist switches.STP BPUs' will not cross layer links.




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