Few scenarios:

ModbusTCP both as a master and slave
ModbusTCP as a master, ModbusRTU as a slave
ModbusTCP as a slave, ModbusRTU as a master

 

What is your question?

Devices with multiple ports normally support any mix of master and slave. For example, a flow meter with 4 serial ports could have 3 configured as slave and 1 master, all 4 as slave, 2 as slave, 2 as master and so on.

On Ethernet, a device can obviously have both 'client/master' and 'server/slave' function enabled at the same time.

 

Don't forget about Modbus RTU firmware Master and Slave concepts. It is a new concept but there are more capabilities than Modbus TCP.

 

>What is your question?
---- snip ---
> On Ethernet, a device can obviously have both 'client/master' and
> 'server/slave' function enabled at the same time.

I was able to answer my question after my posting but thank you for replying. It is appreciated.

 

> Don't forget about Modbus RTU firmware Master and Slave concepts. It is a new
> concept but there are more capabilities than Modbus TCP.

What do you mean? The idea that by looking at the slave address a master/slave can maintain a full-duplex connection mixing master/slave function? the idea that slave_id=1 means master=master and slave=slave, while if slave_id != 1 means master=proxy and slave=master?
http://iatips.wikispaces.com/ModbusRBX

I have seen that on several small waste-water RTU, plus our Modbus 'bridge' devices support that for a single serial 'slave/master' attached.