Originally Posted by dyn
This part completely contradicts the other parts of your post but it is the truth. You really need to start with the basics and work your way up. A lot of vendors have certifications that certify you for their products only. Cisco is such a vendor. They teach you some important stuff but it will be aimed at their products. So if you're working with Juniper equipment it doesn't make sense to get a Cisco certification. It's more helpful to get some Juniper certification instead. Apart from that you don't always need certification. Vendor support sites and other online (and even offline) resources can be enough.
The encryption and hashing algorithms are pretty standardised regardless of platform, as are most of the implementations of 802.1whatever, STP, LACP, OSPF, BGP etc. The Cisco certs teach you about the protocols, THEN
how to implement them on a Cisco platform. Even if you never touch a Cisco device again you will still gain the base knowledge about how networking at the various OSI layers string together, as well as how TCP/IP fits into the OSI model and what you need to do to secure the various protocols within it.
And yes, you can get everything you need for free from the Web if you want. The RFC documents themselves are all publicly there. However, that's not really what I would recommend for someone just starting out, and the OP specifically asked about certs.