As a software dev I don't think you'd be completely wasting your time, only mostly wasting your time. I do think everyone who works in IT benefits from having a basic understanding of ports and protocols, and how switches, routers, and firewalls work. These are the foundations that support and enable everything that happens on a network. However, the CCNA curriculum also contains a lot of Cisco-specific information that you likely won't find useful.
So if taking a CCNA class is the best way to get that knowledge, then I would say go for it. But if you already have that knowledge or can find a better way to get it, then I'd say skip the class.
Thank you for the information.