I understyand that the RB1100 has one physiccal port witch is serial0, but is it possible to use serial1? Is there a pin out on the board to add an extra DB9?
Did you read the manual for the RB1100??? It tells you how to do this. There is a serial header already soldered to the motherboard for connecting a second serial port.
The manual says alternate connector. I am not clear if this connector is for serial1 or if is just an pin to pin replicate of the DB9 serial0? All the RB1100 spec manual are talking of only one serial port available. There is no mention anywhere of a second serial port available (even internal).
Can you confirm that if one is connecting to J402, it is for serial1 and not serial0.
There IS mention of the second serial port! Look at this snippet of the v4.8 changelog…
*) Added support for secondary serial port on RB800/RB1100
if port is available in RouterOS then it is separate port. Does not matter it is serial or some other type of port.
Usually configurations do not talk about second serial as majority of products have only 1 serial port if are having one at all.