I need to connect an MTS2EA to a serial device, then I want to be able to telnet (using port 23) straight through the MTS2EA out of the serial port to my serial device. How can I configure the serial port (S0) as port 23?

You will need to setup Auto-Dialout. The default auto-dialout port is configured for port 5000. See our "howto-autodialout.doc" to setup auto-dialout at:

https://webfiles.multitech.com/resolutions/documents/multiconnect/