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    Multichassis System Configuration

    The BTI7800 supports a multichassis configuration where two BTI7800 chassis can be managed as a single network element. The management planes of the two chassis are connected together by connecting the gigabit Ethernet EXP-1 (expansion) ports on the CMMs in one chassis to the EXP-1 ports on the CMMs in the other chassis. Since there are two CMMs in each chassis, there are two management links connecting the two chassis together (for redundancy). The data planes remain separate in a multichassis system.

    Figure 1: Multiple Chassis Expansion Port

    Multiple Chassis Expansion Port

    The chassis are distinguished by their chassis identifiers. The hub chassis is always chassis:1 while the satellite chassis is chassis:2. The hub chassis provides management connectivity for the system, and controls the satellite chassis. All slot designations remain unchanged. For example, a UFM in slot 3 of the satellite chassis is identified as ufm:2/3.

    All chassis must be equipped with CMMs. The CMMs take on different roles depending on where they reside. In the hub chassis, the CMMs act as active and standby system controller modules (SCMs), similar to a single chassis system. In the satellite chassis, the CMMs act as management relay modules (MRMs), and simply relay internal management traffic to and from the SCMs in the hub chassis. You log in to the active SCM in the hub chassis as you do in a single chassis system, by using the shared management IP address. You cannot log in directly to the MRMs in the satellite chassis. Management of the satellite chassis is performed through the SCMs in the hub chassis.

    The following rules apply in a multichassis configuration:

    • Only chassis of the same type can be connected to each other. A BTI7814 chassis can only be connected to another BTI7814 chassis. A BTI7802 chassis can only be connected to another BTI7802 chassis.
    • The BTI7801 chassis cannot be connected in a multichassis system.
    • The hub chassis contains two CMMs acting as SCMs. The satellite chassis contains two CMMs acting as MRMs.
    • The CMM in slot A in the hub chassis must be connected to the CMM in slot A in the satellite chassis. Similarly, the CMM in slot B in the hub chassis must be connected to the CMM in slot B in the satellite chassis.

    Once the multichassis system is set up, the SCMs in the hub chassis control the traffic modules in both chassis. If the active SCM goes down, the standby SCM takes over.

    If both SCMs go down, the service modules in both chassis detect that SCM connectivity is lost. Service modules continue to pass traffic but do not update counters or raise alarms. This behavior, when both SCMs fail, is the same regardless of whether you are running a single chassis or a multichassis system. See Chassis Management Module Failure for more information.

    Note: For the satellite chassis, SCM connectivity can also be lost due to both inter-chassis links going down. In this situation, the behavior in the satellite chassis is the same as if both SCMs have gone down.

    Modified: 2017-10-24