I have several excellent condition Cisco textbooks that I believe are still useful and which you can have for free - just DM me and I'll ship them to you, and I'll cover shipping 1. Routing TCP/IP Vol 1 2. CCDE Study Guide 3. Optimal Routing Design Let me know

I'd love the CCDE book as networking isn't my primary but i often gotta have ideas anyway, and much is also about interoperability. But, there are no DMs and only if you don't have to pay too much to send it (Germany)