CCNA is important if you’re looking forward for the examinations like CCNP and CCIE. People with CS/IT background also acquire this certificate to put it in their resume as a symbol that they’ve sufficient knowledge about networking and it helps them too.
CCNA is basic. It’s important. It makes you aware of what networking and internet is all about.
If you have sufficient knowledge about networking, then you can start preparing for CCNA. By sufficient i mean that you should have basic knowledge regarding routing algorithms, switching and subnetting.
CCNA is mostly all about basics. It doesn’t involve troubleshooting. So if you’re familiar with IOS (Internetwork Operating System) and can configure router at basic level then you’re good. For the theoretical portion of exam you can always refer to books.
Spending most of your time with configuring routers and switches can give you a slight idea about how connections are made in real life. There are software which provide you almost same GUI and functionality as the real life devices do. Obviously there will be some drawbacks like some commands might not work. But for CCNA level they’re more than perfect.