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SPBm reachability issues with no SMLT implementation

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TitleSPBm reachability issues with no SMLT implementation
Symptoms
Reachability issues reported from certain parts of the network. The topology diagram looks as follows:

User-added image


In the above example, the VSP_1_1 cannot reach the server connected to VSP_2_2.
 
Environment
  • Virtual Services Platforms 
  • All supported software versions
Cause
Although SMLT, to connect the server, is not in use, the VSP_2_1 and VSP_2_2 are clustered using vIST. That means, they share the same vBMAC. You can validate that by issuing below command:

VSP_2_1#show isis spbm

==============================================================================================================
                                                ISIS SPBM Info
==============================================================================================================
SPBM       B-VID      PRIMARY    NICK     LSDB     IP       IPV6     MULTICAST  SPB-PIM-GW         STP-MULTI
INSTANCE              VLAN       NAME     TRAP                                                     HOMING
--------------------------------------------------------------------------------------------------------------
1          3051-3052  3051       1.07.01  disable  enable   disable  enable     disable            disable

==============================================================================================================
                                             ISIS SPBM SMLT Info
==============================================================================================================
SPBM       SMLT-SPLIT-BEB       SMLT-VIRTUAL-BMAC     SMLT-PEER-SYSTEM-ID
INSTANCE
--------------------------------------------------------------------------------------------------------------
1          primary              0a:fd:07:00:01:01    0afd.0700.0200


--------------------------------------------------------------------------------
 Total Num of SPBM instances: 1
--------------------------------------------------------------------------------




VSP_2_2#show isis spbm

====================================================================================================
                                 ISIS SPBM Info
====================================================================================================
SPBM       B-VID      PRIMARY    NICK     LSDB     IP       IPV6     MULTICAST  SPB-PIM-GW
INSTANCE              VLAN       NAME     TRAP
----------------------------------------------------------------------------------------------------
1          3051-3052  3051       1.07.02  disable  enable   disable  disable    disable

====================================================================================================
                              ISIS SPBM SMLT Info
====================================================================================================
SPBM       SMLT-SPLIT-BEB       SMLT-VIRTUAL-BMAC     SMLT-PEER-SYSTEM-ID
INSTANCE
----------------------------------------------------------------------------------------------------
1          secondary            0a:fd:07:00:01:01    0afd.0700.0100


--------------------------------------------------------------------------------
 Total Num of SPBM instances: 1
--------------------------------------------------------------------------------


In the SPBM core, the bridges forward encapsulated traffic based on the BMAC-DA. From the VSP_1_1 perspective(ISIS SPF algorithm), the shortest path to reach BMAC-DA: 0a:fd:07:00:01:01, is through VSP_2_1(as it shares that BMAC). However, VSP_2_1 have no VLAN_10 : I-SID_100010 information, hence traffic for VLAN 10(where the Server resides) is dropped.
 
Resolution
Adding VLAN_10 : I-SID_100010 mapping to VSP_2_1 solves the problem.

To avoid such issues, you should keep VLAN/I-SID database consistent,on both peers, while vIST is in use.
Additional notes

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