Here's a guide on how to instal and set up your GK420d network printer on Mac to use with Shipmondo.
Give your printer a static IP address
Make sure you give your printer a static IP address before setting it up on your Mac. Instruction for this can be found in the printer instruction manual or in other way supplied by the manufacturer.
When the printer is connected to the same network as your computer and you've given your printer a static IP address, you are ready to connect the printer to your Mac.
Set up your label printer
Open the Printers & Scanners setup on your Mac.
Click on the Plus-button (+) in the bottom left corner to add your printer. Then go to the IP tab.
Enter IP Address
Enter your printer's IP address in Address.
Name your printer in Name, e.g. "Zebra GK420d".
Click on the dropdown by Use and click on Select Software.
Select Zebra EPL2 Label Printer from the list.
Click on Add.
A couple of seconds and your label printer is ready for use.
Customize paper size and print your shipping label
Once the printer is set up, select the correct paper size in the print dialog.
A shipping label can be printed directly from your browser.
In the print dialog, create/select the appropriate paper size. e.g. 10×19 cm (actual size 102x192 mm).
Click on Print and your shipping label is now printed and ready for use.