Finding Mac address of Root Bridge

[mahesh18]

                   Hi Everyone,

I was trying to find the mac address of root bridge for vlan 20

DSW1#sh spanning-tree vlan 20

VLAN0020
  Spanning tree enabled protocol rstp
  Root ID    Priority    24596
             Address     001b.90e7.d480*************

             Cost        19
             Port        11 (FastEthernet1/0/9)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    61460  (priority 61440 sys-id-ext 20)
             Address     0019.e849.d380
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------

Fa1/0/9             Root FWD 19        128.11   P2p Peer(STP)

Here it shows that  MAc address of Root bridge is 001b.90e7.d480.

I login to Switch which is root bridge for vlan 20

Core#sh spanning-tree vlan 20

VLAN0020
  Spanning tree enabled protocol ieee
  Root ID    Priority    24596
             Address     001b.90e7.d480
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24596  (priority 24576 sys-id-ext 20)
             Address     001b.90e7.d480
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1          Desg FWD 19        128.1    P2p
Gi1/0/11         Desg FWD 19        128.11   P2p

Core# sh mac ad
Core# sh mac address-table add
Core# sh mac address-table address 001b.90e7.d480
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
Core#

I can not find the mac address 001b.90e7.d480 in the core switch.

Need to know where is this mac and how can i find it inside the switch?

Thanks

Mahesh

[Reza Sharifi · Accepted solution]

Hi Mahesh,

If you issue "sh ver" you should find the base switch MAC address.

You should see something like this:

Base ethernet MAC Address       : 00:1B:44:00:22:80

HTH

Reza

[mahesh18]

Hi Reza,

You were correct seems switch base mac addres is used for STP.

Regards

Mahesh

[garrison.sutton]

I spent all day trying to figure out where to find the Base ethernet MAC Address.  STP is great in theory but it's hard to make sure you understand it in your network if you can't figure out where to get the MAC for your switches!  Thanks, Reza, for this VERY valuable nugget of info! :D  Yeah ... I'm dredging up a 5 year old thread, but thanks anyway!