Re: Root Port issue

Don't forget it is the position of the STP root bridge that will determine
which ports are elected root ports on down stream switch. Which one of the
3750's is acting as root bridge? Which port on 2960 is closest to root
bridge?

On Tuesday, November 5, 2013, ramesh Kumar wrote:

> Hello All,
>
> I have topology like this, I see a problem that the right port is
> not getting selected as the Root Port
>
> 2960 (f0/1)------> 3750-A (G0/1)
> 2960
> (f0/2)------> 3750-B (G0/1)
>
> checking at 2960 i should see f0/1 as RP for any
> Vlan but strangely f0/2 is showing to be the RP despite having higher port
> ID
> than f0/1. Any idea is it because of having fe/ge connectivity?
>
>
> 2960#sh
> spann vlan 136
>
> MST1
> Spanning tree enabled protocol mstp
> Root ID
> Priority 8193
> Address 8478.ac21.b2c1
> Cost
> 202000
> Port 2 (FastEthernet0/2)
> Hello
> Time 2 sec Max Age 20 sec Forward Delay 15 sec
>
> Bridge ID Priority
> 61441 (priority 61440 sys-id-ext 1)
> Address d0c7.899b.6400
> Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
> Interface Role Sts Cost Prio.Nbr Type
> ------------------- ----
> --- --------- -------- --------------------------------
> Fa0/1
> Altn BLK 200000 128.1 P2p
> Fa0/2 Root FWD 200000 128.2
> P2p
>
> config on 2960
> interface FastEthernet0/1
> switchport trunk allowed
> vlan 136,166,176
> switchport mode trunk
> duplex full
> speed 100
> end
>
> config on
> 3750-A
> interface GigabitEthernet0/1
> switchport trunk allowed vlan 136,166,176
> switchport mode trunk
> speed 100
> duplex full
> end
>
> config on 3750-B
> interface
> GigabitEthernet0/1
> switchport trunk allowed vlan 136,166,176
> switchport mode
> trunk
> speed 100
> duplex full
> end
>
> MST config
>
> 3750-A#sh spann mst config
> Name
> []
> Revision 0 Instances configured 2
>
> Instance Vlans mapped
> --------
> ---------------------------------------------------------------------
> 0
> none
> 1 1-4094
>
> -----------------------------------------------------------------------------
> --
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>
>

-- 
Marc Edwards
CCIE #38259
Blogs and organic groups at http://www.ccie.net