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Mastership Election in a Virtual Chassis

In a two-member MX Series Virtual Chassis, either member router can be elected as the master router (also known as the protocol master, or VC-M) of the Virtual Chassis. The first member router to join the Virtual Chassis becomes the initial master router by default. After the Virtual Chassis is formed with both member routers, the Virtual Chassis Control Protocol (VCCP) software runs a mastership election algorithm to elect the master router for the Virtual Chassis configuration.

If the master router in a Virtual Chassis fails, the backup router (also known as the protocol backup, or VC-B) takes over mastership of the Virtual Chassis. You can also switch the global roles of the master router and backup router in a Virtual Chassis by issuing the request virtual-chassis routing-engine master switch command.

Note: You cannot configure mastership election for an MX Series Virtual Chassis in the current release.

1. Choose the member router that has the highest value for the internal mastership election flag.

   The mastership election algorithm uses an internal flag that keeps track of the member state for the purpose of electing the Virtual Chassis master router. In most cases, VCCP elects the member router with the higher flag value over the member router with the lower flag value as the protocol master.

   To display the mastership election flag value, issue the show virtual-chassis protocol database extensive command. The flag value used for mastership election appears in the TLVs field of the command output, as shown in the following example:

   {master:member1-re0}

   user@host> show virtual-chassis protocol database member 0 extensive

    ...
     TLVs:
       Node Info: Member ID: 1, VC ID: 5a6a.e747.8511, Flags: 3, Priority: 129
          System ID: 001d.b510.0800, Device ID: 1
    ...
   

2. Choose the member router with the highest mastership priority value.

   The mastership priority value is assigned to the member router by the VCCP software, and is not configurable in the current release. The mastership priority value can be one of the following:

   • 129—The routing-engine role is assigned to the member router.
   • 128—No role is assigned to the member router.
   • 0—The line-card role is assigned to the member router (not supported in the current release).

   To display the mastership priority value for the member routers in the Virtual Chassis, issue the show virtual-chassis status command.

3. Choose the member router that is active in the Virtual Chassis.
4. Choose the member router that belongs to the Virtual Chassis with the largest number of members.

   Note: This criterion is not used in the current release because all MX Series Virtual Chassis configurations have two member routers.

5. Choose the member router that is the accepted (elected) protocol master of the Virtual Chassis.
6. Choose the member router that is the current protocol master (VC-M) of the same Virtual Chassis.
7. Choose the member router that is the current protocol backup (VC-B) of the same Virtual Chassis.
8. Choose the member router that has been part of the Virtual Chassis configuration for the longest period of time.
9. Choose the member router that was the previous protocol master of the same Virtual Chassis.
10. Choose the member router with the lowest media access control (MAC) address.