Identify the root bridge by determining where the Common and Internal Spanning Tree (CIST) regional root MAC address is learned for the STP-reserved I-SID. Check which MAC address has the same first five octets as the CIST regional root MAC address.
When you enable MSTP-Fabric Connect Multi Homing, you can use the following two commands to determine which BEB is the root bridge:
show spanning-tree mstp status
show i-sid mac-address-entry 16777003
show spanning-tree mstp status
show i-sid mac-address-entry 16777003
In the following example, bold text identifies the relevant information in the command output. In the output of the second command, the DEST-MAC shows 10:cd:ae:6e:d8:84, which is the system ID of the CIST regional root BEB, and the system name is BEB-1000.
Switch:1>show spanning-tree mstp status ========================================================================================== MSTP Status ========================================================================================== ------------------------------------------------------------------------------------------ Bridge Address : b0:ad:aa:4d:b8:00 Cist Root : 80:00:10:cd:ae:6e:d8:00 Cist Regional Root : 80:00:10:cd:ae:6e:d8:00 Cist Root Port : fabric Cist Root Cost : 0 Cist Regional Root Cost : 2000000 Cist Instance Vlan Mapped : 1-1024 Cist Instance Vlan Mapped2k : 1025-2048 Cist Instance Vlan Mapped3k : 2049-3072 Cist Instance Vlan Mapped4k : 3073-4050,4053-4059 Cist Max Age : 20 seconds Cist Forward Delay : 15 seconds
Switch:1>show i-sid mac-address-entry 16777003 ============================================================================================== I-SID Fdb Table ============================================================================================== I-SID STATUS MAC-ADDRESS INTERFACE TYPE DEST-MAC BVLAN DEST-SYSNAME ---------------------------------------------------------------------------------------------- 16777003 learned 10:cd:ae:6e:d8:82 Port-1/9 REMOTE 10:cd:ae:6e:d8:84 4051 BEB-1000 16777003 learned 10:cd:ae:db:a4:83 Port-1/40 REMOTE 10:cd:ae:db:a4:84 4051 7208 16777003 learned b0:ad:aa:40:14:82 Port-1/40 REMOTE b0:ad:aa:40:14:84 4051 6222