So I just installed a new serial port on my PC so I can connect to my switch via console, and while connecting to the switch, I have a connection established but it prints all these weird symbols. Does anyone know how to fix this?

Heres the setup page:

enter image description here

Heres the console:

enter image description here

  • You have a problem with one of the parameters in the second image. The bits received are not lining up with the data bits, stop bits, and/or parity.
    – Ron Maupin
    Nov 14, 2018 at 2:10
  • Most likely, you have the wrong baud rate set.
    – Ron Trunk
    Nov 14, 2018 at 2:44
  • You can check other common Speed, in spite of frequently-used 9600.
    – aircraft
    Nov 14, 2018 at 10:50
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 25, 2018 at 10:01

2 Answers 2


As already answered, it's because you have a mismatch in the speed between the far device and your computer.

  • Just try all the speeds in (my suggested) order: 9600, 1200, 115200, then all the speeds your terminal will allow.
  • As a heuristic, if you get too many characters, try a lower speed; too few, try higher.
  • Use handshaking "none" unless forced otherwise (thanks commenter Andrey).
  • Keep it at 8N1. (If you get the right number of characters but some are wrong and some are right, then you have the right speed but wrong parity, extremely unusual in 2018. Try 7e1, 7o1.)

Just to add that serial ports are for specific purposes, and don't get frustrated if you find it slow, because debugging is always slower than anything else.

It is for this exact reason that many organisations fix a lowest-common denominator speed for serial ports -- often 9600 8N1 -- so that you never spend any time debugging this. The reasoning being if you're using the serial console, you're doing something which is rare and can't be done over the main network.

One organisation I worked with had it on their specifications list: "equipment must be delivered with default serial console speed at 9600/8N1", which could get negotiated down to "equipment must be able to be permanently configured to 9600/8N1".

A number of otherwise-excellent manufacturers lost contracts because of this. I know of one manufacturer which would have won the edge switch contract, but its equipment had fixed 115,200 baud which couldn't be changed -- I wrote to them complaining (2016), I hope they've fixed it now, but they lost all those sales.

  • Also in addition I want to mention that in some cases Flow control should be turned off (had cases with old HP switches). Nov 14, 2018 at 14:21

Serial lines cannot detect the settings of the other side, so you need to match them.

8N1 (8 data bits, no parity, 1 stop bit) is very common and probably correct. Try 19,200 or 38,400 baud.

Most devices don't use flow control at all or software (Xon/Xoff). Hardware flow control is rare (RTS/CTS or even DSR/DTR) and requires a cable with the appropriate pinout. Setting flow control to none usually doesn't hurt - if longer input or output drops characters you can try Xon/Xoff.

(nb: Some serial device actually can auto-detect various settings, esp. the baud rate - inside the terminal, hit [Enter] several times to generate the expected bit sequence so the device may be able to guess the terminal's rate.)

  • 1
    Also you can try these: 1200 , 2400 , 57600 , 115200 Nov 14, 2018 at 7:55

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