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Switchover Behavior in a Virtual Chassis

Virtual Chassis Role Transitions During a Global Switchover

To change the mastership in an MX Series or Virtual Chassis and cause a global switchover, you issue the request virtual-chassis routing-engine master switch command from the master router or switch. After you issue this command, the current master router or switch in the Virtual Chassis (VC-M) becomes the backup router or switch(VC-B), and the current backup router or switch (VC-B) becomes the master router or switch (VC-M).

A global switchover in an MX Series or Virtual Chassis causes the role transitions listed in Table 1.

The local roles (master and standby, or m and s) of the Routing Engines do not change after a global switchover. For example, as shown in Table 1, the master Routing Engine in the Virtual Chassis backup router or switch (VC-Bm) remains the master Routing Engine in the Virtual Chassis master router or switch (VC-Mm) after the global switchover.

Virtual Chassis Role Transitions During a Local Switchover

To ensure redundancy in a two-member Virtual Chassis configuration, each of the two member routers or switches must be configured with dual Routing Engines. To toggle local mastership between the master Routing Engine and the standby Routing Engine in the member router or switch, you issue the request chassis routing-engine master switch command.

A local switchover in a Virtual Chassis causes the role transitions listed in Table 2.

The local roles (master and standby, or m and s) of the Routing Engines in the Virtual Chassis master router or switch change after a local switchover, but the local roles of the Routing Engines in the Virtual Chassis backup router or switch do not change. For example, as shown in Table 2, the master Routing Engine in the Virtual Chassis master router or switch (VC-Mm) becomes the standby Routing Engine in the Virtual Chassis backup router or switch (VC-Bs) after the local switchover. By contrast, the master Routing Engine in the Virtual Chassis backup router or switch (VC-Bm) remains the master Routing Engine in the Virtual Chassis master router or switch (VC-Mm) after the local switchover.

GRES Readiness in a Virtual Chassis Configuration

Depending on the configuration, a variable amount of time is required before a router or switch is ready to perform a graceful Routing Engine switchover (GRES). Attempting a GRES operation before the router or switch is ready can cause system errors and unexpected behavior. To determine whether the member routers or switches in an MX Series or Virtual Chassis configuration are ready for a GRES operation from a database synchronization perspective, you can issue the request virtual-chassis routing-engine master switch check command from the Virtual Chassis master router or switch (VC-Mm) before you initiate the GRES operation.

The request virtual-chassis routing-engine master switch check command checks various system and database components on the member routers or switches to determine whether they are ready for GRES, but does not initiate the global GRES operation itself. The readiness check includes ensuring that a system timer, which expires after 300 seconds, has completed before the global GRES operation can begin.

Using the request virtual-chassis routing-engine master switch check command before you initiate the GRES operation ensures that the subscriber management and kernel databases on both member routers or switches in an MX Series or Virtual Chassis are synchronized and ready for the GRES operation.