Yes, you can take the Network+ certification exam without an A+ certification. Network+ certification is for getting into the Networking domain, and A+ is for becoming service technicians dealing with issues in a computer or a mobile device. With Network+ certification, you can get an entry-level job in the Networking domain.
Take up the CompTIA Network+ Training from Intellipaat and boost your chances of clearing the Network+ certification. Also, watch the following video on Network Security Basics to get a better understanding.