Serial console access to Cisco devices with macOS screen

Today brought me one step closer to being completely dongle free on my Mac and standardizing on one type of cable connection. Upon receiving my USB-C Cisco console cable I decided to experiemnt using the screen terminal app and go beyond the basics of console port connectivity to understanding screen’s other features.

Displaying the device name

The first thing to do when connecting the USB-C console cable is identify the device name of the cable itself. The command ls /dev will list all devices connected to my MacBook Pro but since this is a USB serial cable I will use *usbser* to minimize the results.

Without the cable connected to my Mac

ls /dev/*usbser*

ls: /dev/*usbser*: No such file or directory

With the cable connected to my Mac

ls /dev/*usbser*

/dev/cu.usbserial-AH06ORDE

And there it is!

Console connectivity

This tells terminal to use 9600 baud rate. Note that 8N1 is already the default asynchronous mode.

$ screen /dev/cu.usbserial-AH06ORDE 9600

Time to power on the router.

System Bootstrap, Version 16.9(1r), RELEASE SOFTWARE
Copyright (c) 1994-2018  by cisco Systems, Inc.


Current image running: Boot ROM0

Last reset cause: PowerOn
C1111-8PWB platform with 4194304 Kbytes of main memory

Success! Screen has an active console connection to my router

Pressing CTRL-A then ? shows the screen menu

Additional screen commands

CTRL-A then c will create another console window

CTRL-A then SHIFT-A will allow renaming the current console

CTRL-A then " display both terminals

CTRL-A then n or p moves to next or previous windows

CTRL-A then SHIFT-S displays the terminals as split screen

CTRL-A then Tab toggles between split screen windows

CTRL-A then i identifies which is the active window

Open another terminal window to list all active screen sessions

$ screen -list
There is a screen on:
	93529.ttys001.2594	(Attached)
1 Socket in /var/folders/sb/7dkxrqcs32z948hv4zpxjzfx5cxpbq/T/.screen.

CTRL-A then d detaches from the session and display the terminal prompt

To re-attach to a screen session, or if you accidentally close terminal and need to get back to your console session.

$ screen -r

Create .screenrc if it does not exist

cd ~
touch .screenrc

Edit .screenrc to add custom startup message or disable with startup_message off.