Re: Root Port issue

Can you provide 'sh span vlan 136' for all devices?

Marc Edwards
CCIE #38259

On Tue, Nov 5, 2013 at 10:18 PM, Rati Berikaant Jokhadze
<iinfo83_at_gmail.com>wrote:

> 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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>>
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Received on Wed Nov 06 2013 - 11:37:59 ART