I follow the Tutorial to connect a switch,

use ls *usb* I can find the usb:

$ ls *usb*

I connect to it:

screen tty.wchusbserial1410 9600

but I get the messy code when I type the keyboard.

I type enter, there gets the ?, I type s, there will get f. you can see in the snapshot:


My switch is Juniper-EX4300 and the usb driver is Qinheng.

and the Juniper manual shows the Baud rate is 9600.


I use the console-serial line connect the switch port, and then use the serial-USB convertor connect the line and my Mac.

  • This is because of speed mismatch between your console and the device you try to connect to. You have to know on which speed your device is communicating and set this speed to your terminal program. Also good to know is number of data-bits, stop-bits and parity. Aug 2, 2018 at 12:59
  • @WinnieTigger Do you mean the switch's console port ?
    – aircraft
    Aug 2, 2018 at 13:02
  • Yes! On what speed etc. is the switch console set? This parameters need to be the same in your terminal programm. Aug 2, 2018 at 13:03
  • how to see the switch console port? and in the manual the Juniper EX4300 is 9600, I use this rate connect you can see in my post.
    – aircraft
    Aug 2, 2018 at 13:05
  • Is this a new device? If not, maybe someone changed it. Aug 2, 2018 at 13:07

1 Answer 1


Serial port settings mismatch. Please set serial setting as below:

  • Baud rate—9600
  • Flow control—None
  • Data—8
  • Parity—None
  • Stop bits—1
  • DCD state—Disregard
  • whats then command of the settings with ‘screen’?
    – aircraft
    Aug 2, 2018 at 16:10
  • try 9600,cs8,-ixon,-ixoff Aug 2, 2018 at 16:15
  • this do not work, bro.
    – aircraft
    Aug 3, 2018 at 2:48

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