Spanning Root bridge identification

[mahadeer md ismail]

Hi All,

I checked one design and did not able to find the root bridge for the vlan

Design is:

Sw1----Sw2 (Po1- Gi1/41(P)  & Gi1/42(P)  connected back to back to these switches) i did not notice any output which says, This bridge is the root

here is the log :

Sw 1:

show spanning-tree vlan 28

VLAN0028

  Spanning tree enabled protocol ieee

  Root ID    Priority    8220

             Address     0015.2c61.6000

             Cost        16

             Port        48 (GigabitEthernet1/48)

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32796  (priority 32768 sys-id-ext 28)

             Address     5475.d034.da40

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type

------------------- ---- --- --------- -------- --------------------------------

Po1                 Desg FWD 3         128.641  P2p

Sw2:

show spanning-tree vlan 28

VLAN0028

  Spanning tree enabled protocol ieee

  Root ID    Priority    8220

             Address     0015.2c61.6000

             Cost        16

             Port        48 (GigabitEthernet1/48)

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32796  (priority 32768 sys-id-ext 28)

             Address     5475.d034.ddc0

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type

------------------- ---- --- --------- -------- --------------------------------

Po1                 Altn BLK 3         128.641  P2p

Please let me know what kind of scenario is this ? and how we can find the root bridge on this ?

Thanks

[aukhadiev]

According to the output of the command, the root bridge is 0015.2c61.6000... According MAC OUI the vendor of this MAC is Cisco Systems... Have you any router with switch module in this design, conected to the switch1 and switch2? Apparently, this the switch module on this router is the root?

p.s. ... although I am embarrassed by the lack of lines in the output type - "interface" Root FWD etc... Is it the full output of the "show spanning-tree vlan 28" ?

What say - show spanning-tree root? show spanning-tree summary?

[InayathUlla Sharieff]

MAhadeer,

Actualy tthis should be automatically detected based on the bridge id information. (Highest priority  if brk then using mac address).

Do one thing can you just add this command on the SW1 and update me the result?

SW1 # config t

SW1# spanning-tree vlan 28 root primary

Now check the STP status you should have your sw1 primary.

Also if possible share the config files from both the switches.

REgards

Inayath

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