If you have to upload firmware to a router or a switch with xmodem, get the package ⇒lrzsz-0.12.20.tar.gz.
First, install Xcode from the App Store.
Then compile the package and install it.
tar xvzf lrzsz-0.12.20.tar.gz cd lrzsz-0.12.20 ./configure --disable-nls && sudo make install
Next, start a console session with screen
screen /dev/tty.Keyserial1 9600
When you are asked from the program to upload the firmware using xmodem, do:
Press ctrl-a :exec !! lsx -b -X /path/srw2016-24-10086.ros
The upload will start.
Don’t be surprised. This software is very old and the upload takes forever.