We are facing problem to connect the Garmin GPS 18x USB with a (USB female to RJ-45 adapter) to iDirect X5 Modem using version iDx 2.1.1,

Step 1:
We have configure the remote terminal as below,

Mobile:
GPS Input:
Baud Rate = 4800
Data = 8
Parity = None
Stop bit = 1
Sample(Sec) = 120

What port on the iDirect are you using for GPS?  Console or (GPIO)?  

If your X5 supports it, you really need to consider wiring/piloting GPS/NMEA to the high density (GPIO) port on the backplane of the iDirect.  It is better suited for GPS and using that port allows for a seamless transition from Redboot to falcon when your specified (opt) GPS port speed differs from that of Redboot (9600).  I have noted NUMEROUS hangups when using GPS on console when feeding GPS at 4800 on console (esp when redboot is 9600).  

That, or if you are determined to use console (to feed GPS) you need to consider changing the redboot port speed to 4800 to mitigate that redboot to falcon transition.  Make sense?