Yes CCNA will surely help in understanding the fundamentals of networking as you said. As far as front end development concern, CCNA, is best option for you, as you don't have much information regarding network concepts. CCNA trains you the fundamental concepts of networking and related networking concepts on Cisco technology.

Having a certification separate you from other non-certified networking people in your company. It'll not provide you job in exact way, bt it increase your chances to get that job.Going for SCJP, for a well experienced java developer is not a better option.It s better to go for SCJD, rather than going for SCJP.

But if you want to go into networking domain, then there is no need to think to go for Sun Certification.

From my point of view, certifications just place you at a top priority to get a job but it does not guarantee you a job. CCNA teaches you the fundamentals of networking and concepts related Network engineering using CISCO technology. If your job scope demands you to know networking concepts and you have no exposure please go for CCNA. SCJP won't come very much in handy for an experienced Java developer. I did my SCJP before getting into the job market. It does place me at the top priority to get my first job and also improved my Java fundamentals. Since you don't have much exposure on Networking I would suggest go for CCNA, it will improve your fundamentals.

It is a recognized cert in the job market and will land you a better paying job out of the gate. If you want more information, then you may visit GTSS - it has planned its certificate courses in such a way that it makes IT aspirants not only academically strong but also proficient in their particular discipline. This makes them capable in all respects to meet industry requirements.