Schneider Electric Modbus Plus Network Bridge Multiplexer none - Manual (Page 49)

Configuring the Modbus Models 31007492 39
Silent Master Port Considerations
In the Silent Master port configuration, one Modbus master device and
one or more Modbus slave devices can be connected as a Modbus
network at the port. This allows the master device to address the slave
devices directly, as well as to address other devices at other ports on the
same BM85 or across Modbus Plus.
In the Silent Master configuration, the slave devices on the port must
have unique addresses in your application. They must not be the same
as a node address (1 ... 64) on the BM85's local Modbus Plus network.
They must also not exist as entries in the Modbus Address Map table
that you setup within the BM85.
The Modbus addresses in the master's queries to the slave devices at the
Silent Master port must not map beyond the port -- not to any routing
path on Modbus Plus, nor to another port on the BM85.