I am always favorable of anyone who wants to take cert tests. You never know when they could come in handy. I am currently working on my CCNA, probably go to CCNP or CCSP.
Here is what I am hearing from you. You are considering getting the CCNA cert for a promotion or raise at your current position. You work with switches, are they Cisco? If you get this cert do you think you boss will give you a raise or promotion, will you get to work with anything new? Are you thinking that if you get this cert maybe you could help with the voip? Here's the deal, if you think you could get to do more stuff with routers or the voip by obtaining the cert, or you would leave and go somewhere where you could do that then go for it. If your boss doesn't have any extra duties or more advanced work to give you, obtainig the cert might not do any good there. It could always help somewhere else though. As for how much it is worth it is hard to say. It really depends on if you get a new position there, or just a bump to your curreny salary.
Network Admin
A+, Network+, MCSA 2000, MCSE 2000