Hello:
I am using a redundant Rx3i with max-on, on both racks I have GBCs, Profibus DP masters and modbus masters, for the switching of profibus I'll have to use a switching relays controlled by a digital outputs to switch over when the mastership change, any body has better idea for switching the Profibus other than using the relays....

Thanks

This what you're looking for ?

Profibus Redundancy Link module

I took a look at the module in the past, to my knowledge the module will detect the failure in one network and switch to the other one automatically, I do not know how could this help, because in my system when the mastership change from one PLC to the other one the profibus module which resides on the secondary PLC is still active and trying to pull the slaves even if the seconday PLC in error or stop mode (meaning there will be no reason for the module to switch to the other network) and because both the PB masters are trying to pull the same slaves we need to have physical disconnection between the slaves and the profibus module which resides on the secondary, that's why I am using the relays.
now I am not sure if you mean to use the module instead of the relays in this case there should be a way to control the enable and disable of the networks based on the mastership status the PLCs (may be using a digital output ).

Thanks

Well I asumed when the mastership changes over the Profibus master would have failed as well. But if you are talking about changing mastership when the other unit is still healthy then you should look for something that can actively change to another channel by command.
Of course using switching relays will probably work just as well.

http://www.comsoft.de/html/icpe/profibus/switch/prs.htm