The secondary ID of the bridge domain supported by this entity. This field is only valid if pimTmEntSnoopBridgeDomainType is 'vpws' or 'vpls'. The interpretation of this value depends upon the value of pimTmEntSnoopBridgeDomainType, as follows. - For 'vpws', this is the AC interface index. - For 'vpls', this is the VPLS site index. The type of bridge domain might impose additional restrictions on the valid range of this field. This field is only relevant for MGMD snooping. Otherwise, this value has no effect. If this configuration is changed whilst the entity is active, the entity will be deactivated, and restarted using the new value.