Re: Root Port issue

could you please send , show spanning-tree interface fa0/1 & fa 0/2
output results.

thanks

On 11/06/2013 09:31 AM, ramesh Kumar wrote:
> HI Marc,
>
> The root bridge the core switch 6509-A is at equal distance from
> 2960. I you try to draw the topology diagram with the below mention points it
> will give you the picture. the root bridge 6509-A is 2 hops away from from the
> 2960 so ideally f0/1 shoud be selected as the root port in 2960 because of
> lower port ID but instead f0/2 is getting selected as the root port.
>
> 2960
> (f0/1)------> 3750-A (G0/1) 3750-A (T1/49)-----> 6509-A (Root Bridge)
>
> 3750-A (T1/50)-----> 6509-B
> 2960 (f0/2)------> 3750-B (G0/1) 3750-B (T1/49)-----> 6509-A (Root Bridge)
>
>
> 3750-B (T1/50)-----> 6509-B
>
>
>
> On
> Wednesday, November 6, 2013 10:02 AM, marc edwards <renorider_at_gmail.com>
> wrote:
>
> 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
>> -----------------------------------------------------------------------------
>> --
>>
>>
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Received on Wed Nov 06 2013 - 10:18:42 ART